diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 5032 |
1 files changed, 5032 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c new file mode 100644 index 0000000000..bfc5cff0e1 --- /dev/null +++ b/fs/namespace.c @@ -0,0 +1,5032 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * linux/fs/namespace.c + * + * (C) Copyright Al Viro 2000, 2001 + * + * Based on code from fs/super.c, copyright Linus Torvalds and others. + * Heavily rewritten. + */ + +#include <linux/syscalls.h> +#include <linux/export.h> +#include <linux/capability.h> +#include <linux/mnt_namespace.h> +#include <linux/user_namespace.h> +#include <linux/namei.h> +#include <linux/security.h> +#include <linux/cred.h> +#include <linux/idr.h> +#include <linux/init.h> /* init_rootfs */ +#include <linux/fs_struct.h> /* get_fs_root et.al. */ +#include <linux/fsnotify.h> /* fsnotify_vfsmount_delete */ +#include <linux/file.h> +#include <linux/uaccess.h> +#include <linux/proc_ns.h> +#include <linux/magic.h> +#include <linux/memblock.h> +#include <linux/proc_fs.h> +#include <linux/task_work.h> +#include <linux/sched/task.h> +#include <uapi/linux/mount.h> +#include <linux/fs_context.h> +#include <linux/shmem_fs.h> +#include <linux/mnt_idmapping.h> + +#include "pnode.h" +#include "internal.h" + +/* Maximum number of mounts in a mount namespace */ +static unsigned int sysctl_mount_max __read_mostly = 100000; + +static unsigned int m_hash_mask __read_mostly; +static unsigned int m_hash_shift __read_mostly; +static unsigned int mp_hash_mask __read_mostly; +static unsigned int mp_hash_shift __read_mostly; + +static __initdata unsigned long mhash_entries; +static int __init set_mhash_entries(char *str) +{ + if (!str) + return 0; + mhash_entries = simple_strtoul(str, &str, 0); + return 1; +} +__setup("mhash_entries=", set_mhash_entries); + +static __initdata unsigned long mphash_entries; +static int __init set_mphash_entries(char *str) +{ + if (!str) + return 0; + mphash_entries = simple_strtoul(str, &str, 0); + return 1; +} +__setup("mphash_entries=", set_mphash_entries); + +static u64 event; +static DEFINE_IDA(mnt_id_ida); +static DEFINE_IDA(mnt_group_ida); + +static struct hlist_head *mount_hashtable __read_mostly; +static struct hlist_head *mountpoint_hashtable __read_mostly; +static struct kmem_cache *mnt_cache __read_mostly; +static DECLARE_RWSEM(namespace_sem); +static HLIST_HEAD(unmounted); /* protected by namespace_sem */ +static LIST_HEAD(ex_mountpoints); /* protected by namespace_sem */ + +struct mount_kattr { + unsigned int attr_set; + unsigned int attr_clr; + unsigned int propagation; + unsigned int lookup_flags; + bool recurse; + struct user_namespace *mnt_userns; + struct mnt_idmap *mnt_idmap; +}; + +/* /sys/fs */ +struct kobject *fs_kobj; +EXPORT_SYMBOL_GPL(fs_kobj); + +/* + * vfsmount lock may be taken for read to prevent changes to the + * vfsmount hash, ie. during mountpoint lookups or walking back + * up the tree. + * + * It should be taken for write in all cases where the vfsmount + * tree or hash is modified or when a vfsmount structure is modified. + */ +__cacheline_aligned_in_smp DEFINE_SEQLOCK(mount_lock); + +static inline void lock_mount_hash(void) +{ + write_seqlock(&mount_lock); +} + +static inline void unlock_mount_hash(void) +{ + write_sequnlock(&mount_lock); +} + +static inline struct hlist_head *m_hash(struct vfsmount *mnt, struct dentry *dentry) +{ + unsigned long tmp = ((unsigned long)mnt / L1_CACHE_BYTES); + tmp += ((unsigned long)dentry / L1_CACHE_BYTES); + tmp = tmp + (tmp >> m_hash_shift); + return &mount_hashtable[tmp & m_hash_mask]; +} + +static inline struct hlist_head *mp_hash(struct dentry *dentry) +{ + unsigned long tmp = ((unsigned long)dentry / L1_CACHE_BYTES); + tmp = tmp + (tmp >> mp_hash_shift); + return &mountpoint_hashtable[tmp & mp_hash_mask]; +} + +static int mnt_alloc_id(struct mount *mnt) +{ + int res = ida_alloc(&mnt_id_ida, GFP_KERNEL); + + if (res < 0) + return res; + mnt->mnt_id = res; + return 0; +} + +static void mnt_free_id(struct mount *mnt) +{ + ida_free(&mnt_id_ida, mnt->mnt_id); +} + +/* + * Allocate a new peer group ID + */ +static int mnt_alloc_group_id(struct mount *mnt) +{ + int res = ida_alloc_min(&mnt_group_ida, 1, GFP_KERNEL); + + if (res < 0) + return res; + mnt->mnt_group_id = res; + return 0; +} + +/* + * Release a peer group ID + */ +void mnt_release_group_id(struct mount *mnt) +{ + ida_free(&mnt_group_ida, mnt->mnt_group_id); + mnt->mnt_group_id = 0; +} + +/* + * vfsmount lock must be held for read + */ +static inline void mnt_add_count(struct mount *mnt, int n) +{ +#ifdef CONFIG_SMP + this_cpu_add(mnt->mnt_pcp->mnt_count, n); +#else + preempt_disable(); + mnt->mnt_count += n; + preempt_enable(); +#endif +} + +/* + * vfsmount lock must be held for write + */ +int mnt_get_count(struct mount *mnt) +{ +#ifdef CONFIG_SMP + int count = 0; + int cpu; + + for_each_possible_cpu(cpu) { + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_count; + } + + return count; +#else + return mnt->mnt_count; +#endif +} + +static struct mount *alloc_vfsmnt(const char *name) +{ + struct mount *mnt = kmem_cache_zalloc(mnt_cache, GFP_KERNEL); + if (mnt) { + int err; + + err = mnt_alloc_id(mnt); + if (err) + goto out_free_cache; + + if (name) { + mnt->mnt_devname = kstrdup_const(name, + GFP_KERNEL_ACCOUNT); + if (!mnt->mnt_devname) + goto out_free_id; + } + +#ifdef CONFIG_SMP + mnt->mnt_pcp = alloc_percpu(struct mnt_pcp); + if (!mnt->mnt_pcp) + goto out_free_devname; + + this_cpu_add(mnt->mnt_pcp->mnt_count, 1); +#else + mnt->mnt_count = 1; + mnt->mnt_writers = 0; +#endif + + INIT_HLIST_NODE(&mnt->mnt_hash); + INIT_LIST_HEAD(&mnt->mnt_child); + INIT_LIST_HEAD(&mnt->mnt_mounts); + INIT_LIST_HEAD(&mnt->mnt_list); + INIT_LIST_HEAD(&mnt->mnt_expire); + INIT_LIST_HEAD(&mnt->mnt_share); + INIT_LIST_HEAD(&mnt->mnt_slave_list); + INIT_LIST_HEAD(&mnt->mnt_slave); + INIT_HLIST_NODE(&mnt->mnt_mp_list); + INIT_LIST_HEAD(&mnt->mnt_umounting); + INIT_HLIST_HEAD(&mnt->mnt_stuck_children); + mnt->mnt.mnt_idmap = &nop_mnt_idmap; + } + return mnt; + +#ifdef CONFIG_SMP +out_free_devname: + kfree_const(mnt->mnt_devname); +#endif +out_free_id: + mnt_free_id(mnt); +out_free_cache: + kmem_cache_free(mnt_cache, mnt); + return NULL; +} + +/* + * Most r/o checks on a fs are for operations that take + * discrete amounts of time, like a write() or unlink(). + * We must keep track of when those operations start + * (for permission checks) and when they end, so that + * we can determine when writes are able to occur to + * a filesystem. + */ +/* + * __mnt_is_readonly: check whether a mount is read-only + * @mnt: the mount to check for its write status + * + * This shouldn't be used directly ouside of the VFS. + * It does not guarantee that the filesystem will stay + * r/w, just that it is right *now*. This can not and + * should not be used in place of IS_RDONLY(inode). + * mnt_want/drop_write() will _keep_ the filesystem + * r/w. + */ +bool __mnt_is_readonly(struct vfsmount *mnt) +{ + return (mnt->mnt_flags & MNT_READONLY) || sb_rdonly(mnt->mnt_sb); +} +EXPORT_SYMBOL_GPL(__mnt_is_readonly); + +static inline void mnt_inc_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + this_cpu_inc(mnt->mnt_pcp->mnt_writers); +#else + mnt->mnt_writers++; +#endif +} + +static inline void mnt_dec_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + this_cpu_dec(mnt->mnt_pcp->mnt_writers); +#else + mnt->mnt_writers--; +#endif +} + +static unsigned int mnt_get_writers(struct mount *mnt) +{ +#ifdef CONFIG_SMP + unsigned int count = 0; + int cpu; + + for_each_possible_cpu(cpu) { + count += per_cpu_ptr(mnt->mnt_pcp, cpu)->mnt_writers; + } + + return count; +#else + return mnt->mnt_writers; +#endif +} + +static int mnt_is_readonly(struct vfsmount *mnt) +{ + if (READ_ONCE(mnt->mnt_sb->s_readonly_remount)) + return 1; + /* + * The barrier pairs with the barrier in sb_start_ro_state_change() + * making sure if we don't see s_readonly_remount set yet, we also will + * not see any superblock / mount flag changes done by remount. + * It also pairs with the barrier in sb_end_ro_state_change() + * assuring that if we see s_readonly_remount already cleared, we will + * see the values of superblock / mount flags updated by remount. + */ + smp_rmb(); + return __mnt_is_readonly(mnt); +} + +/* + * Most r/o & frozen checks on a fs are for operations that take discrete + * amounts of time, like a write() or unlink(). We must keep track of when + * those operations start (for permission checks) and when they end, so that we + * can determine when writes are able to occur to a filesystem. + */ +/** + * __mnt_want_write - get write access to a mount without freeze protection + * @m: the mount on which to take a write + * + * This tells the low-level filesystem that a write is about to be performed to + * it, and makes sure that writes are allowed (mnt it read-write) before + * returning success. This operation does not protect against filesystem being + * frozen. When the write operation is finished, __mnt_drop_write() must be + * called. This is effectively a refcount. + */ +int __mnt_want_write(struct vfsmount *m) +{ + struct mount *mnt = real_mount(m); + int ret = 0; + + preempt_disable(); + mnt_inc_writers(mnt); + /* + * The store to mnt_inc_writers must be visible before we pass + * MNT_WRITE_HOLD loop below, so that the slowpath can see our + * incremented count after it has set MNT_WRITE_HOLD. + */ + smp_mb(); + might_lock(&mount_lock.lock); + while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) { + if (!IS_ENABLED(CONFIG_PREEMPT_RT)) { + cpu_relax(); + } else { + /* + * This prevents priority inversion, if the task + * setting MNT_WRITE_HOLD got preempted on a remote + * CPU, and it prevents life lock if the task setting + * MNT_WRITE_HOLD has a lower priority and is bound to + * the same CPU as the task that is spinning here. + */ + preempt_enable(); + lock_mount_hash(); + unlock_mount_hash(); + preempt_disable(); + } + } + /* + * The barrier pairs with the barrier sb_start_ro_state_change() making + * sure that if we see MNT_WRITE_HOLD cleared, we will also see + * s_readonly_remount set (or even SB_RDONLY / MNT_READONLY flags) in + * mnt_is_readonly() and bail in case we are racing with remount + * read-only. + */ + smp_rmb(); + if (mnt_is_readonly(m)) { + mnt_dec_writers(mnt); + ret = -EROFS; + } + preempt_enable(); + + return ret; +} + +/** + * mnt_want_write - get write access to a mount + * @m: the mount on which to take a write + * + * This tells the low-level filesystem that a write is about to be performed to + * it, and makes sure that writes are allowed (mount is read-write, filesystem + * is not frozen) before returning success. When the write operation is + * finished, mnt_drop_write() must be called. This is effectively a refcount. + */ +int mnt_want_write(struct vfsmount *m) +{ + int ret; + + sb_start_write(m->mnt_sb); + ret = __mnt_want_write(m); + if (ret) + sb_end_write(m->mnt_sb); + return ret; +} +EXPORT_SYMBOL_GPL(mnt_want_write); + +/** + * __mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like __mnt_want_write, but if the file is already open for writing it + * skips incrementing mnt_writers (since the open file already has a reference) + * and instead only does the check for emergency r/o remounts. This must be + * paired with __mnt_drop_write_file. + */ +int __mnt_want_write_file(struct file *file) +{ + if (file->f_mode & FMODE_WRITER) { + /* + * Superblock may have become readonly while there are still + * writable fd's, e.g. due to a fs error with errors=remount-ro + */ + if (__mnt_is_readonly(file->f_path.mnt)) + return -EROFS; + return 0; + } + return __mnt_want_write(file->f_path.mnt); +} + +/** + * mnt_want_write_file - get write access to a file's mount + * @file: the file who's mount on which to take a write + * + * This is like mnt_want_write, but if the file is already open for writing it + * skips incrementing mnt_writers (since the open file already has a reference) + * and instead only does the freeze protection and the check for emergency r/o + * remounts. This must be paired with mnt_drop_write_file. + */ +int mnt_want_write_file(struct file *file) +{ + int ret; + + sb_start_write(file_inode(file)->i_sb); + ret = __mnt_want_write_file(file); + if (ret) + sb_end_write(file_inode(file)->i_sb); + return ret; +} +EXPORT_SYMBOL_GPL(mnt_want_write_file); + +/** + * __mnt_drop_write - give up write access to a mount + * @mnt: the mount on which to give up write access + * + * Tells the low-level filesystem that we are done + * performing writes to it. Must be matched with + * __mnt_want_write() call above. + */ +void __mnt_drop_write(struct vfsmount *mnt) +{ + preempt_disable(); + mnt_dec_writers(real_mount(mnt)); + preempt_enable(); +} + +/** + * mnt_drop_write - give up write access to a mount + * @mnt: the mount on which to give up write access + * + * Tells the low-level filesystem that we are done performing writes to it and + * also allows filesystem to be frozen again. Must be matched with + * mnt_want_write() call above. + */ +void mnt_drop_write(struct vfsmount *mnt) +{ + __mnt_drop_write(mnt); + sb_end_write(mnt->mnt_sb); +} +EXPORT_SYMBOL_GPL(mnt_drop_write); + +void __mnt_drop_write_file(struct file *file) +{ + if (!(file->f_mode & FMODE_WRITER)) + __mnt_drop_write(file->f_path.mnt); +} + +void mnt_drop_write_file(struct file *file) +{ + __mnt_drop_write_file(file); + sb_end_write(file_inode(file)->i_sb); +} +EXPORT_SYMBOL(mnt_drop_write_file); + +/** + * mnt_hold_writers - prevent write access to the given mount + * @mnt: mnt to prevent write access to + * + * Prevents write access to @mnt if there are no active writers for @mnt. + * This function needs to be called and return successfully before changing + * properties of @mnt that need to remain stable for callers with write access + * to @mnt. + * + * After this functions has been called successfully callers must pair it with + * a call to mnt_unhold_writers() in order to stop preventing write access to + * @mnt. + * + * Context: This function expects lock_mount_hash() to be held serializing + * setting MNT_WRITE_HOLD. + * Return: On success 0 is returned. + * On error, -EBUSY is returned. + */ +static inline int mnt_hold_writers(struct mount *mnt) +{ + mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; + /* + * After storing MNT_WRITE_HOLD, we'll read the counters. This store + * should be visible before we do. + */ + smp_mb(); + + /* + * With writers on hold, if this value is zero, then there are + * definitely no active writers (although held writers may subsequently + * increment the count, they'll have to wait, and decrement it after + * seeing MNT_READONLY). + * + * It is OK to have counter incremented on one CPU and decremented on + * another: the sum will add up correctly. The danger would be when we + * sum up each counter, if we read a counter before it is incremented, + * but then read another CPU's count which it has been subsequently + * decremented from -- we would see more decrements than we should. + * MNT_WRITE_HOLD protects against this scenario, because + * mnt_want_write first increments count, then smp_mb, then spins on + * MNT_WRITE_HOLD, so it can't be decremented by another CPU while + * we're counting up here. + */ + if (mnt_get_writers(mnt) > 0) + return -EBUSY; + + return 0; +} + +/** + * mnt_unhold_writers - stop preventing write access to the given mount + * @mnt: mnt to stop preventing write access to + * + * Stop preventing write access to @mnt allowing callers to gain write access + * to @mnt again. + * + * This function can only be called after a successful call to + * mnt_hold_writers(). + * + * Context: This function expects lock_mount_hash() to be held. + */ +static inline void mnt_unhold_writers(struct mount *mnt) +{ + /* + * MNT_READONLY must become visible before ~MNT_WRITE_HOLD, so writers + * that become unheld will see MNT_READONLY. + */ + smp_wmb(); + mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; +} + +static int mnt_make_readonly(struct mount *mnt) +{ + int ret; + + ret = mnt_hold_writers(mnt); + if (!ret) + mnt->mnt.mnt_flags |= MNT_READONLY; + mnt_unhold_writers(mnt); + return ret; +} + +int sb_prepare_remount_readonly(struct super_block *sb) +{ + struct mount *mnt; + int err = 0; + + /* Racy optimization. Recheck the counter under MNT_WRITE_HOLD */ + if (atomic_long_read(&sb->s_remove_count)) + return -EBUSY; + + lock_mount_hash(); + list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { + if (!(mnt->mnt.mnt_flags & MNT_READONLY)) { + err = mnt_hold_writers(mnt); + if (err) + break; + } + } + if (!err && atomic_long_read(&sb->s_remove_count)) + err = -EBUSY; + + if (!err) + sb_start_ro_state_change(sb); + list_for_each_entry(mnt, &sb->s_mounts, mnt_instance) { + if (mnt->mnt.mnt_flags & MNT_WRITE_HOLD) + mnt->mnt.mnt_flags &= ~MNT_WRITE_HOLD; + } + unlock_mount_hash(); + + return err; +} + +static void free_vfsmnt(struct mount *mnt) +{ + mnt_idmap_put(mnt_idmap(&mnt->mnt)); + kfree_const(mnt->mnt_devname); +#ifdef CONFIG_SMP + free_percpu(mnt->mnt_pcp); +#endif + kmem_cache_free(mnt_cache, mnt); +} + +static void delayed_free_vfsmnt(struct rcu_head *head) +{ + free_vfsmnt(container_of(head, struct mount, mnt_rcu)); +} + +/* call under rcu_read_lock */ +int __legitimize_mnt(struct vfsmount *bastard, unsigned seq) +{ + struct mount *mnt; + if (read_seqretry(&mount_lock, seq)) + return 1; + if (bastard == NULL) + return 0; + mnt = real_mount(bastard); + mnt_add_count(mnt, 1); + smp_mb(); // see mntput_no_expire() + if (likely(!read_seqretry(&mount_lock, seq))) + return 0; + if (bastard->mnt_flags & MNT_SYNC_UMOUNT) { + mnt_add_count(mnt, -1); + return 1; + } + lock_mount_hash(); + if (unlikely(bastard->mnt_flags & MNT_DOOMED)) { + mnt_add_count(mnt, -1); + unlock_mount_hash(); + return 1; + } + unlock_mount_hash(); + /* caller will mntput() */ + return -1; +} + +/* call under rcu_read_lock */ +static bool legitimize_mnt(struct vfsmount *bastard, unsigned seq) +{ + int res = __legitimize_mnt(bastard, seq); + if (likely(!res)) + return true; + if (unlikely(res < 0)) { + rcu_read_unlock(); + mntput(bastard); + rcu_read_lock(); + } + return false; +} + +/** + * __lookup_mnt - find first child mount + * @mnt: parent mount + * @dentry: mountpoint + * + * If @mnt has a child mount @c mounted @dentry find and return it. + * + * Note that the child mount @c need not be unique. There are cases + * where shadow mounts are created. For example, during mount + * propagation when a source mount @mnt whose root got overmounted by a + * mount @o after path lookup but before @namespace_sem could be + * acquired gets copied and propagated. So @mnt gets copied including + * @o. When @mnt is propagated to a destination mount @d that already + * has another mount @n mounted at the same mountpoint then the source + * mount @mnt will be tucked beneath @n, i.e., @n will be mounted on + * @mnt and @mnt mounted on @d. Now both @n and @o are mounted at @mnt + * on @dentry. + * + * Return: The first child of @mnt mounted @dentry or NULL. + */ +struct mount *__lookup_mnt(struct vfsmount *mnt, struct dentry *dentry) +{ + struct hlist_head *head = m_hash(mnt, dentry); + struct mount *p; + + hlist_for_each_entry_rcu(p, head, mnt_hash) + if (&p->mnt_parent->mnt == mnt && p->mnt_mountpoint == dentry) + return p; + return NULL; +} + +/* + * lookup_mnt - Return the first child mount mounted at path + * + * "First" means first mounted chronologically. If you create the + * following mounts: + * + * mount /dev/sda1 /mnt + * mount /dev/sda2 /mnt + * mount /dev/sda3 /mnt + * + * Then lookup_mnt() on the base /mnt dentry in the root mount will + * return successively the root dentry and vfsmount of /dev/sda1, then + * /dev/sda2, then /dev/sda3, then NULL. + * + * lookup_mnt takes a reference to the found vfsmount. + */ +struct vfsmount *lookup_mnt(const struct path *path) +{ + struct mount *child_mnt; + struct vfsmount *m; + unsigned seq; + + rcu_read_lock(); + do { + seq = read_seqbegin(&mount_lock); + child_mnt = __lookup_mnt(path->mnt, path->dentry); + m = child_mnt ? &child_mnt->mnt : NULL; + } while (!legitimize_mnt(m, seq)); + rcu_read_unlock(); + return m; +} + +static inline void lock_ns_list(struct mnt_namespace *ns) +{ + spin_lock(&ns->ns_lock); +} + +static inline void unlock_ns_list(struct mnt_namespace *ns) +{ + spin_unlock(&ns->ns_lock); +} + +static inline bool mnt_is_cursor(struct mount *mnt) +{ + return mnt->mnt.mnt_flags & MNT_CURSOR; +} + +/* + * __is_local_mountpoint - Test to see if dentry is a mountpoint in the + * current mount namespace. + * + * The common case is dentries are not mountpoints at all and that + * test is handled inline. For the slow case when we are actually + * dealing with a mountpoint of some kind, walk through all of the + * mounts in the current mount namespace and test to see if the dentry + * is a mountpoint. + * + * The mount_hashtable is not usable in the context because we + * need to identify all mounts that may be in the current mount + * namespace not just a mount that happens to have some specified + * parent mount. + */ +bool __is_local_mountpoint(struct dentry *dentry) +{ + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + struct mount *mnt; + bool is_covered = false; + + down_read(&namespace_sem); + lock_ns_list(ns); + list_for_each_entry(mnt, &ns->list, mnt_list) { + if (mnt_is_cursor(mnt)) + continue; + is_covered = (mnt->mnt_mountpoint == dentry); + if (is_covered) + break; + } + unlock_ns_list(ns); + up_read(&namespace_sem); + + return is_covered; +} + +static struct mountpoint *lookup_mountpoint(struct dentry *dentry) +{ + struct hlist_head *chain = mp_hash(dentry); + struct mountpoint *mp; + + hlist_for_each_entry(mp, chain, m_hash) { + if (mp->m_dentry == dentry) { + mp->m_count++; + return mp; + } + } + return NULL; +} + +static struct mountpoint *get_mountpoint(struct dentry *dentry) +{ + struct mountpoint *mp, *new = NULL; + int ret; + + if (d_mountpoint(dentry)) { + /* might be worth a WARN_ON() */ + if (d_unlinked(dentry)) + return ERR_PTR(-ENOENT); +mountpoint: + read_seqlock_excl(&mount_lock); + mp = lookup_mountpoint(dentry); + read_sequnlock_excl(&mount_lock); + if (mp) + goto done; + } + + if (!new) + new = kmalloc(sizeof(struct mountpoint), GFP_KERNEL); + if (!new) + return ERR_PTR(-ENOMEM); + + + /* Exactly one processes may set d_mounted */ + ret = d_set_mounted(dentry); + + /* Someone else set d_mounted? */ + if (ret == -EBUSY) + goto mountpoint; + + /* The dentry is not available as a mountpoint? */ + mp = ERR_PTR(ret); + if (ret) + goto done; + + /* Add the new mountpoint to the hash table */ + read_seqlock_excl(&mount_lock); + new->m_dentry = dget(dentry); + new->m_count = 1; + hlist_add_head(&new->m_hash, mp_hash(dentry)); + INIT_HLIST_HEAD(&new->m_list); + read_sequnlock_excl(&mount_lock); + + mp = new; + new = NULL; +done: + kfree(new); + return mp; +} + +/* + * vfsmount lock must be held. Additionally, the caller is responsible + * for serializing calls for given disposal list. + */ +static void __put_mountpoint(struct mountpoint *mp, struct list_head *list) +{ + if (!--mp->m_count) { + struct dentry *dentry = mp->m_dentry; + BUG_ON(!hlist_empty(&mp->m_list)); + spin_lock(&dentry->d_lock); + dentry->d_flags &= ~DCACHE_MOUNTED; + spin_unlock(&dentry->d_lock); + dput_to_list(dentry, list); + hlist_del(&mp->m_hash); + kfree(mp); + } +} + +/* called with namespace_lock and vfsmount lock */ +static void put_mountpoint(struct mountpoint *mp) +{ + __put_mountpoint(mp, &ex_mountpoints); +} + +static inline int check_mnt(struct mount *mnt) +{ + return mnt->mnt_ns == current->nsproxy->mnt_ns; +} + +/* + * vfsmount lock must be held for write + */ +static void touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns) { + ns->event = ++event; + wake_up_interruptible(&ns->poll); + } +} + +/* + * vfsmount lock must be held for write + */ +static void __touch_mnt_namespace(struct mnt_namespace *ns) +{ + if (ns && ns->event != event) { + ns->event = event; + wake_up_interruptible(&ns->poll); + } +} + +/* + * vfsmount lock must be held for write + */ +static struct mountpoint *unhash_mnt(struct mount *mnt) +{ + struct mountpoint *mp; + mnt->mnt_parent = mnt; + mnt->mnt_mountpoint = mnt->mnt.mnt_root; + list_del_init(&mnt->mnt_child); + hlist_del_init_rcu(&mnt->mnt_hash); + hlist_del_init(&mnt->mnt_mp_list); + mp = mnt->mnt_mp; + mnt->mnt_mp = NULL; + return mp; +} + +/* + * vfsmount lock must be held for write + */ +static void umount_mnt(struct mount *mnt) +{ + put_mountpoint(unhash_mnt(mnt)); +} + +/* + * vfsmount lock must be held for write + */ +void mnt_set_mountpoint(struct mount *mnt, + struct mountpoint *mp, + struct mount *child_mnt) +{ + mp->m_count++; + mnt_add_count(mnt, 1); /* essentially, that's mntget */ + child_mnt->mnt_mountpoint = mp->m_dentry; + child_mnt->mnt_parent = mnt; + child_mnt->mnt_mp = mp; + hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); +} + +/** + * mnt_set_mountpoint_beneath - mount a mount beneath another one + * + * @new_parent: the source mount + * @top_mnt: the mount beneath which @new_parent is mounted + * @new_mp: the new mountpoint of @top_mnt on @new_parent + * + * Remove @top_mnt from its current mountpoint @top_mnt->mnt_mp and + * parent @top_mnt->mnt_parent and mount it on top of @new_parent at + * @new_mp. And mount @new_parent on the old parent and old + * mountpoint of @top_mnt. + * + * Context: This function expects namespace_lock() and lock_mount_hash() + * to have been acquired in that order. + */ +static void mnt_set_mountpoint_beneath(struct mount *new_parent, + struct mount *top_mnt, + struct mountpoint *new_mp) +{ + struct mount *old_top_parent = top_mnt->mnt_parent; + struct mountpoint *old_top_mp = top_mnt->mnt_mp; + + mnt_set_mountpoint(old_top_parent, old_top_mp, new_parent); + mnt_change_mountpoint(new_parent, new_mp, top_mnt); +} + + +static void __attach_mnt(struct mount *mnt, struct mount *parent) +{ + hlist_add_head_rcu(&mnt->mnt_hash, + m_hash(&parent->mnt, mnt->mnt_mountpoint)); + list_add_tail(&mnt->mnt_child, &parent->mnt_mounts); +} + +/** + * attach_mnt - mount a mount, attach to @mount_hashtable and parent's + * list of child mounts + * @parent: the parent + * @mnt: the new mount + * @mp: the new mountpoint + * @beneath: whether to mount @mnt beneath or on top of @parent + * + * If @beneath is false, mount @mnt at @mp on @parent. Then attach @mnt + * to @parent's child mount list and to @mount_hashtable. + * + * If @beneath is true, remove @mnt from its current parent and + * mountpoint and mount it on @mp on @parent, and mount @parent on the + * old parent and old mountpoint of @mnt. Finally, attach @parent to + * @mnt_hashtable and @parent->mnt_parent->mnt_mounts. + * + * Note, when __attach_mnt() is called @mnt->mnt_parent already points + * to the correct parent. + * + * Context: This function expects namespace_lock() and lock_mount_hash() + * to have been acquired in that order. + */ +static void attach_mnt(struct mount *mnt, struct mount *parent, + struct mountpoint *mp, bool beneath) +{ + if (beneath) + mnt_set_mountpoint_beneath(mnt, parent, mp); + else + mnt_set_mountpoint(parent, mp, mnt); + /* + * Note, @mnt->mnt_parent has to be used. If @mnt was mounted + * beneath @parent then @mnt will need to be attached to + * @parent's old parent, not @parent. IOW, @mnt->mnt_parent + * isn't the same mount as @parent. + */ + __attach_mnt(mnt, mnt->mnt_parent); +} + +void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) +{ + struct mountpoint *old_mp = mnt->mnt_mp; + struct mount *old_parent = mnt->mnt_parent; + + list_del_init(&mnt->mnt_child); + hlist_del_init(&mnt->mnt_mp_list); + hlist_del_init_rcu(&mnt->mnt_hash); + + attach_mnt(mnt, parent, mp, false); + + put_mountpoint(old_mp); + mnt_add_count(old_parent, -1); +} + +/* + * vfsmount lock must be held for write + */ +static void commit_tree(struct mount *mnt) +{ + struct mount *parent = mnt->mnt_parent; + struct mount *m; + LIST_HEAD(head); + struct mnt_namespace *n = parent->mnt_ns; + + BUG_ON(parent == mnt); + + list_add_tail(&head, &mnt->mnt_list); + list_for_each_entry(m, &head, mnt_list) + m->mnt_ns = n; + + list_splice(&head, n->list.prev); + + n->mounts += n->pending_mounts; + n->pending_mounts = 0; + + __attach_mnt(mnt, parent); + touch_mnt_namespace(n); +} + +static struct mount *next_mnt(struct mount *p, struct mount *root) +{ + struct list_head *next = p->mnt_mounts.next; + if (next == &p->mnt_mounts) { + while (1) { + if (p == root) + return NULL; + next = p->mnt_child.next; + if (next != &p->mnt_parent->mnt_mounts) + break; + p = p->mnt_parent; + } + } + return list_entry(next, struct mount, mnt_child); +} + +static struct mount *skip_mnt_tree(struct mount *p) +{ + struct list_head *prev = p->mnt_mounts.prev; + while (prev != &p->mnt_mounts) { + p = list_entry(prev, struct mount, mnt_child); + prev = p->mnt_mounts.prev; + } + return p; +} + +/** + * vfs_create_mount - Create a mount for a configured superblock + * @fc: The configuration context with the superblock attached + * + * Create a mount to an already configured superblock. If necessary, the + * caller should invoke vfs_get_tree() before calling this. + * + * Note that this does not attach the mount to anything. + */ +struct vfsmount *vfs_create_mount(struct fs_context *fc) +{ + struct mount *mnt; + + if (!fc->root) + return ERR_PTR(-EINVAL); + + mnt = alloc_vfsmnt(fc->source ?: "none"); + if (!mnt) + return ERR_PTR(-ENOMEM); + + if (fc->sb_flags & SB_KERNMOUNT) + mnt->mnt.mnt_flags = MNT_INTERNAL; + + atomic_inc(&fc->root->d_sb->s_active); + mnt->mnt.mnt_sb = fc->root->d_sb; + mnt->mnt.mnt_root = dget(fc->root); + mnt->mnt_mountpoint = mnt->mnt.mnt_root; + mnt->mnt_parent = mnt; + + lock_mount_hash(); + list_add_tail(&mnt->mnt_instance, &mnt->mnt.mnt_sb->s_mounts); + unlock_mount_hash(); + return &mnt->mnt; +} +EXPORT_SYMBOL(vfs_create_mount); + +struct vfsmount *fc_mount(struct fs_context *fc) +{ + int err = vfs_get_tree(fc); + if (!err) { + up_write(&fc->root->d_sb->s_umount); + return vfs_create_mount(fc); + } + return ERR_PTR(err); +} +EXPORT_SYMBOL(fc_mount); + +struct vfsmount *vfs_kern_mount(struct file_system_type *type, + int flags, const char *name, + void *data) +{ + struct fs_context *fc; + struct vfsmount *mnt; + int ret = 0; + + if (!type) + return ERR_PTR(-EINVAL); + + fc = fs_context_for_mount(type, flags); + if (IS_ERR(fc)) + return ERR_CAST(fc); + + if (name) + ret = vfs_parse_fs_string(fc, "source", + name, strlen(name)); + if (!ret) + ret = parse_monolithic_mount_data(fc, data); + if (!ret) + mnt = fc_mount(fc); + else + mnt = ERR_PTR(ret); + + put_fs_context(fc); + return mnt; +} +EXPORT_SYMBOL_GPL(vfs_kern_mount); + +struct vfsmount * +vfs_submount(const struct dentry *mountpoint, struct file_system_type *type, + const char *name, void *data) +{ + /* Until it is worked out how to pass the user namespace + * through from the parent mount to the submount don't support + * unprivileged mounts with submounts. + */ + if (mountpoint->d_sb->s_user_ns != &init_user_ns) + return ERR_PTR(-EPERM); + + return vfs_kern_mount(type, SB_SUBMOUNT, name, data); +} +EXPORT_SYMBOL_GPL(vfs_submount); + +static struct mount *clone_mnt(struct mount *old, struct dentry *root, + int flag) +{ + struct super_block *sb = old->mnt.mnt_sb; + struct mount *mnt; + int err; + + mnt = alloc_vfsmnt(old->mnt_devname); + if (!mnt) + return ERR_PTR(-ENOMEM); + + if (flag & (CL_SLAVE | CL_PRIVATE | CL_SHARED_TO_SLAVE)) + mnt->mnt_group_id = 0; /* not a peer of original */ + else + mnt->mnt_group_id = old->mnt_group_id; + + if ((flag & CL_MAKE_SHARED) && !mnt->mnt_group_id) { + err = mnt_alloc_group_id(mnt); + if (err) + goto out_free; + } + + mnt->mnt.mnt_flags = old->mnt.mnt_flags; + mnt->mnt.mnt_flags &= ~(MNT_WRITE_HOLD|MNT_MARKED|MNT_INTERNAL); + + atomic_inc(&sb->s_active); + mnt->mnt.mnt_idmap = mnt_idmap_get(mnt_idmap(&old->mnt)); + + mnt->mnt.mnt_sb = sb; + mnt->mnt.mnt_root = dget(root); + mnt->mnt_mountpoint = mnt->mnt.mnt_root; + mnt->mnt_parent = mnt; + lock_mount_hash(); + list_add_tail(&mnt->mnt_instance, &sb->s_mounts); + unlock_mount_hash(); + + if ((flag & CL_SLAVE) || + ((flag & CL_SHARED_TO_SLAVE) && IS_MNT_SHARED(old))) { + list_add(&mnt->mnt_slave, &old->mnt_slave_list); + mnt->mnt_master = old; + CLEAR_MNT_SHARED(mnt); + } else if (!(flag & CL_PRIVATE)) { + if ((flag & CL_MAKE_SHARED) || IS_MNT_SHARED(old)) + list_add(&mnt->mnt_share, &old->mnt_share); + if (IS_MNT_SLAVE(old)) + list_add(&mnt->mnt_slave, &old->mnt_slave); + mnt->mnt_master = old->mnt_master; + } else { + CLEAR_MNT_SHARED(mnt); + } + if (flag & CL_MAKE_SHARED) + set_mnt_shared(mnt); + + /* stick the duplicate mount on the same expiry list + * as the original if that was on one */ + if (flag & CL_EXPIRE) { + if (!list_empty(&old->mnt_expire)) + list_add(&mnt->mnt_expire, &old->mnt_expire); + } + + return mnt; + + out_free: + mnt_free_id(mnt); + free_vfsmnt(mnt); + return ERR_PTR(err); +} + +static void cleanup_mnt(struct mount *mnt) +{ + struct hlist_node *p; + struct mount *m; + /* + * The warning here probably indicates that somebody messed + * up a mnt_want/drop_write() pair. If this happens, the + * filesystem was probably unable to make r/w->r/o transitions. + * The locking used to deal with mnt_count decrement provides barriers, + * so mnt_get_writers() below is safe. + */ + WARN_ON(mnt_get_writers(mnt)); + if (unlikely(mnt->mnt_pins.first)) + mnt_pin_kill(mnt); + hlist_for_each_entry_safe(m, p, &mnt->mnt_stuck_children, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } + fsnotify_vfsmount_delete(&mnt->mnt); + dput(mnt->mnt.mnt_root); + deactivate_super(mnt->mnt.mnt_sb); + mnt_free_id(mnt); + call_rcu(&mnt->mnt_rcu, delayed_free_vfsmnt); +} + +static void __cleanup_mnt(struct rcu_head *head) +{ + cleanup_mnt(container_of(head, struct mount, mnt_rcu)); +} + +static LLIST_HEAD(delayed_mntput_list); +static void delayed_mntput(struct work_struct *unused) +{ + struct llist_node *node = llist_del_all(&delayed_mntput_list); + struct mount *m, *t; + + llist_for_each_entry_safe(m, t, node, mnt_llist) + cleanup_mnt(m); +} +static DECLARE_DELAYED_WORK(delayed_mntput_work, delayed_mntput); + +static void mntput_no_expire(struct mount *mnt) +{ + LIST_HEAD(list); + int count; + + rcu_read_lock(); + if (likely(READ_ONCE(mnt->mnt_ns))) { + /* + * Since we don't do lock_mount_hash() here, + * ->mnt_ns can change under us. However, if it's + * non-NULL, then there's a reference that won't + * be dropped until after an RCU delay done after + * turning ->mnt_ns NULL. So if we observe it + * non-NULL under rcu_read_lock(), the reference + * we are dropping is not the final one. + */ + mnt_add_count(mnt, -1); + rcu_read_unlock(); + return; + } + lock_mount_hash(); + /* + * make sure that if __legitimize_mnt() has not seen us grab + * mount_lock, we'll see their refcount increment here. + */ + smp_mb(); + mnt_add_count(mnt, -1); + count = mnt_get_count(mnt); + if (count != 0) { + WARN_ON(count < 0); + rcu_read_unlock(); + unlock_mount_hash(); + return; + } + if (unlikely(mnt->mnt.mnt_flags & MNT_DOOMED)) { + rcu_read_unlock(); + unlock_mount_hash(); + return; + } + mnt->mnt.mnt_flags |= MNT_DOOMED; + rcu_read_unlock(); + + list_del(&mnt->mnt_instance); + + if (unlikely(!list_empty(&mnt->mnt_mounts))) { + struct mount *p, *tmp; + list_for_each_entry_safe(p, tmp, &mnt->mnt_mounts, mnt_child) { + __put_mountpoint(unhash_mnt(p), &list); + hlist_add_head(&p->mnt_umount, &mnt->mnt_stuck_children); + } + } + unlock_mount_hash(); + shrink_dentry_list(&list); + + if (likely(!(mnt->mnt.mnt_flags & MNT_INTERNAL))) { + struct task_struct *task = current; + if (likely(!(task->flags & PF_KTHREAD))) { + init_task_work(&mnt->mnt_rcu, __cleanup_mnt); + if (!task_work_add(task, &mnt->mnt_rcu, TWA_RESUME)) + return; + } + if (llist_add(&mnt->mnt_llist, &delayed_mntput_list)) + schedule_delayed_work(&delayed_mntput_work, 1); + return; + } + cleanup_mnt(mnt); +} + +void mntput(struct vfsmount *mnt) +{ + if (mnt) { + struct mount *m = real_mount(mnt); + /* avoid cacheline pingpong, hope gcc doesn't get "smart" */ + if (unlikely(m->mnt_expiry_mark)) + m->mnt_expiry_mark = 0; + mntput_no_expire(m); + } +} +EXPORT_SYMBOL(mntput); + +struct vfsmount *mntget(struct vfsmount *mnt) +{ + if (mnt) + mnt_add_count(real_mount(mnt), 1); + return mnt; +} +EXPORT_SYMBOL(mntget); + +/* + * Make a mount point inaccessible to new lookups. + * Because there may still be current users, the caller MUST WAIT + * for an RCU grace period before destroying the mount point. + */ +void mnt_make_shortterm(struct vfsmount *mnt) +{ + if (mnt) + real_mount(mnt)->mnt_ns = NULL; +} + +/** + * path_is_mountpoint() - Check if path is a mount in the current namespace. + * @path: path to check + * + * d_mountpoint() can only be used reliably to establish if a dentry is + * not mounted in any namespace and that common case is handled inline. + * d_mountpoint() isn't aware of the possibility there may be multiple + * mounts using a given dentry in a different namespace. This function + * checks if the passed in path is a mountpoint rather than the dentry + * alone. + */ +bool path_is_mountpoint(const struct path *path) +{ + unsigned seq; + bool res; + + if (!d_mountpoint(path->dentry)) + return false; + + rcu_read_lock(); + do { + seq = read_seqbegin(&mount_lock); + res = __path_is_mountpoint(path); + } while (read_seqretry(&mount_lock, seq)); + rcu_read_unlock(); + + return res; +} +EXPORT_SYMBOL(path_is_mountpoint); + +struct vfsmount *mnt_clone_internal(const struct path *path) +{ + struct mount *p; + p = clone_mnt(real_mount(path->mnt), path->dentry, CL_PRIVATE); + if (IS_ERR(p)) + return ERR_CAST(p); + p->mnt.mnt_flags |= MNT_INTERNAL; + return &p->mnt; +} + +#ifdef CONFIG_PROC_FS +static struct mount *mnt_list_next(struct mnt_namespace *ns, + struct list_head *p) +{ + struct mount *mnt, *ret = NULL; + + lock_ns_list(ns); + list_for_each_continue(p, &ns->list) { + mnt = list_entry(p, typeof(*mnt), mnt_list); + if (!mnt_is_cursor(mnt)) { + ret = mnt; + break; + } + } + unlock_ns_list(ns); + + return ret; +} + +/* iterator; we want it to have access to namespace_sem, thus here... */ +static void *m_start(struct seq_file *m, loff_t *pos) +{ + struct proc_mounts *p = m->private; + struct list_head *prev; + + down_read(&namespace_sem); + if (!*pos) { + prev = &p->ns->list; + } else { + prev = &p->cursor.mnt_list; + + /* Read after we'd reached the end? */ + if (list_empty(prev)) + return NULL; + } + + return mnt_list_next(p->ns, prev); +} + +static void *m_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct proc_mounts *p = m->private; + struct mount *mnt = v; + + ++*pos; + return mnt_list_next(p->ns, &mnt->mnt_list); +} + +static void m_stop(struct seq_file *m, void *v) +{ + struct proc_mounts *p = m->private; + struct mount *mnt = v; + + lock_ns_list(p->ns); + if (mnt) + list_move_tail(&p->cursor.mnt_list, &mnt->mnt_list); + else + list_del_init(&p->cursor.mnt_list); + unlock_ns_list(p->ns); + up_read(&namespace_sem); +} + +static int m_show(struct seq_file *m, void *v) +{ + struct proc_mounts *p = m->private; + struct mount *r = v; + return p->show(m, &r->mnt); +} + +const struct seq_operations mounts_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = m_show, +}; + +void mnt_cursor_del(struct mnt_namespace *ns, struct mount *cursor) +{ + down_read(&namespace_sem); + lock_ns_list(ns); + list_del(&cursor->mnt_list); + unlock_ns_list(ns); + up_read(&namespace_sem); +} +#endif /* CONFIG_PROC_FS */ + +/** + * may_umount_tree - check if a mount tree is busy + * @m: root of mount tree + * + * This is called to check if a tree of mounts has any + * open files, pwds, chroots or sub mounts that are + * busy. + */ +int may_umount_tree(struct vfsmount *m) +{ + struct mount *mnt = real_mount(m); + int actual_refs = 0; + int minimum_refs = 0; + struct mount *p; + BUG_ON(!m); + + /* write lock needed for mnt_get_count */ + lock_mount_hash(); + for (p = mnt; p; p = next_mnt(p, mnt)) { + actual_refs += mnt_get_count(p); + minimum_refs += 2; + } + unlock_mount_hash(); + + if (actual_refs > minimum_refs) + return 0; + + return 1; +} + +EXPORT_SYMBOL(may_umount_tree); + +/** + * may_umount - check if a mount point is busy + * @mnt: root of mount + * + * This is called to check if a mount point has any + * open files, pwds, chroots or sub mounts. If the + * mount has sub mounts this will return busy + * regardless of whether the sub mounts are busy. + * + * Doesn't take quota and stuff into account. IOW, in some cases it will + * give false negatives. The main reason why it's here is that we need + * a non-destructive way to look for easily umountable filesystems. + */ +int may_umount(struct vfsmount *mnt) +{ + int ret = 1; + down_read(&namespace_sem); + lock_mount_hash(); + if (propagate_mount_busy(real_mount(mnt), 2)) + ret = 0; + unlock_mount_hash(); + up_read(&namespace_sem); + return ret; +} + +EXPORT_SYMBOL(may_umount); + +static void namespace_unlock(void) +{ + struct hlist_head head; + struct hlist_node *p; + struct mount *m; + LIST_HEAD(list); + + hlist_move_list(&unmounted, &head); + list_splice_init(&ex_mountpoints, &list); + + up_write(&namespace_sem); + + shrink_dentry_list(&list); + + if (likely(hlist_empty(&head))) + return; + + synchronize_rcu_expedited(); + + hlist_for_each_entry_safe(m, p, &head, mnt_umount) { + hlist_del(&m->mnt_umount); + mntput(&m->mnt); + } +} + +static inline void namespace_lock(void) +{ + down_write(&namespace_sem); +} + +enum umount_tree_flags { + UMOUNT_SYNC = 1, + UMOUNT_PROPAGATE = 2, + UMOUNT_CONNECTED = 4, +}; + +static bool disconnect_mount(struct mount *mnt, enum umount_tree_flags how) +{ + /* Leaving mounts connected is only valid for lazy umounts */ + if (how & UMOUNT_SYNC) + return true; + + /* A mount without a parent has nothing to be connected to */ + if (!mnt_has_parent(mnt)) + return true; + + /* Because the reference counting rules change when mounts are + * unmounted and connected, umounted mounts may not be + * connected to mounted mounts. + */ + if (!(mnt->mnt_parent->mnt.mnt_flags & MNT_UMOUNT)) + return true; + + /* Has it been requested that the mount remain connected? */ + if (how & UMOUNT_CONNECTED) + return false; + + /* Is the mount locked such that it needs to remain connected? */ + if (IS_MNT_LOCKED(mnt)) + return false; + + /* By default disconnect the mount */ + return true; +} + +/* + * mount_lock must be held + * namespace_sem must be held for write + */ +static void umount_tree(struct mount *mnt, enum umount_tree_flags how) +{ + LIST_HEAD(tmp_list); + struct mount *p; + + if (how & UMOUNT_PROPAGATE) + propagate_mount_unlock(mnt); + + /* Gather the mounts to umount */ + for (p = mnt; p; p = next_mnt(p, mnt)) { + p->mnt.mnt_flags |= MNT_UMOUNT; + list_move(&p->mnt_list, &tmp_list); + } + + /* Hide the mounts from mnt_mounts */ + list_for_each_entry(p, &tmp_list, mnt_list) { + list_del_init(&p->mnt_child); + } + + /* Add propogated mounts to the tmp_list */ + if (how & UMOUNT_PROPAGATE) + propagate_umount(&tmp_list); + + while (!list_empty(&tmp_list)) { + struct mnt_namespace *ns; + bool disconnect; + p = list_first_entry(&tmp_list, struct mount, mnt_list); + list_del_init(&p->mnt_expire); + list_del_init(&p->mnt_list); + ns = p->mnt_ns; + if (ns) { + ns->mounts--; + __touch_mnt_namespace(ns); + } + p->mnt_ns = NULL; + if (how & UMOUNT_SYNC) + p->mnt.mnt_flags |= MNT_SYNC_UMOUNT; + + disconnect = disconnect_mount(p, how); + if (mnt_has_parent(p)) { + mnt_add_count(p->mnt_parent, -1); + if (!disconnect) { + /* Don't forget about p */ + list_add_tail(&p->mnt_child, &p->mnt_parent->mnt_mounts); + } else { + umount_mnt(p); + } + } + change_mnt_propagation(p, MS_PRIVATE); + if (disconnect) + hlist_add_head(&p->mnt_umount, &unmounted); + } +} + +static void shrink_submounts(struct mount *mnt); + +static int do_umount_root(struct super_block *sb) +{ + int ret = 0; + + down_write(&sb->s_umount); + if (!sb_rdonly(sb)) { + struct fs_context *fc; + + fc = fs_context_for_reconfigure(sb->s_root, SB_RDONLY, + SB_RDONLY); + if (IS_ERR(fc)) { + ret = PTR_ERR(fc); + } else { + ret = parse_monolithic_mount_data(fc, NULL); + if (!ret) + ret = reconfigure_super(fc); + put_fs_context(fc); + } + } + up_write(&sb->s_umount); + return ret; +} + +static int do_umount(struct mount *mnt, int flags) +{ + struct super_block *sb = mnt->mnt.mnt_sb; + int retval; + + retval = security_sb_umount(&mnt->mnt, flags); + if (retval) + return retval; + + /* + * Allow userspace to request a mountpoint be expired rather than + * unmounting unconditionally. Unmount only happens if: + * (1) the mark is already set (the mark is cleared by mntput()) + * (2) the usage count == 1 [parent vfsmount] + 1 [sys_umount] + */ + if (flags & MNT_EXPIRE) { + if (&mnt->mnt == current->fs->root.mnt || + flags & (MNT_FORCE | MNT_DETACH)) + return -EINVAL; + + /* + * probably don't strictly need the lock here if we examined + * all race cases, but it's a slowpath. + */ + lock_mount_hash(); + if (mnt_get_count(mnt) != 2) { + unlock_mount_hash(); + return -EBUSY; + } + unlock_mount_hash(); + + if (!xchg(&mnt->mnt_expiry_mark, 1)) + return -EAGAIN; + } + + /* + * If we may have to abort operations to get out of this + * mount, and they will themselves hold resources we must + * allow the fs to do things. In the Unix tradition of + * 'Gee thats tricky lets do it in userspace' the umount_begin + * might fail to complete on the first run through as other tasks + * must return, and the like. Thats for the mount program to worry + * about for the moment. + */ + + if (flags & MNT_FORCE && sb->s_op->umount_begin) { + sb->s_op->umount_begin(sb); + } + + /* + * No sense to grab the lock for this test, but test itself looks + * somewhat bogus. Suggestions for better replacement? + * Ho-hum... In principle, we might treat that as umount + switch + * to rootfs. GC would eventually take care of the old vfsmount. + * Actually it makes sense, especially if rootfs would contain a + * /reboot - static binary that would close all descriptors and + * call reboot(9). Then init(8) could umount root and exec /reboot. + */ + if (&mnt->mnt == current->fs->root.mnt && !(flags & MNT_DETACH)) { + /* + * Special case for "unmounting" root ... + * we just try to remount it readonly. + */ + if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) + return -EPERM; + return do_umount_root(sb); + } + + namespace_lock(); + lock_mount_hash(); + + /* Recheck MNT_LOCKED with the locks held */ + retval = -EINVAL; + if (mnt->mnt.mnt_flags & MNT_LOCKED) + goto out; + + event++; + if (flags & MNT_DETACH) { + if (!list_empty(&mnt->mnt_list)) + umount_tree(mnt, UMOUNT_PROPAGATE); + retval = 0; + } else { + shrink_submounts(mnt); + retval = -EBUSY; + if (!propagate_mount_busy(mnt, 2)) { + if (!list_empty(&mnt->mnt_list)) + umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); + retval = 0; + } + } +out: + unlock_mount_hash(); + namespace_unlock(); + return retval; +} + +/* + * __detach_mounts - lazily unmount all mounts on the specified dentry + * + * During unlink, rmdir, and d_drop it is possible to loose the path + * to an existing mountpoint, and wind up leaking the mount. + * detach_mounts allows lazily unmounting those mounts instead of + * leaking them. + * + * The caller may hold dentry->d_inode->i_mutex. + */ +void __detach_mounts(struct dentry *dentry) +{ + struct mountpoint *mp; + struct mount *mnt; + + namespace_lock(); + lock_mount_hash(); + mp = lookup_mountpoint(dentry); + if (!mp) + goto out_unlock; + + event++; + while (!hlist_empty(&mp->m_list)) { + mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list); + if (mnt->mnt.mnt_flags & MNT_UMOUNT) { + umount_mnt(mnt); + hlist_add_head(&mnt->mnt_umount, &unmounted); + } + else umount_tree(mnt, UMOUNT_CONNECTED); + } + put_mountpoint(mp); +out_unlock: + unlock_mount_hash(); + namespace_unlock(); +} + +/* + * Is the caller allowed to modify his namespace? + */ +bool may_mount(void) +{ + return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); +} + +/** + * path_mounted - check whether path is mounted + * @path: path to check + * + * Determine whether @path refers to the root of a mount. + * + * Return: true if @path is the root of a mount, false if not. + */ +static inline bool path_mounted(const struct path *path) +{ + return path->mnt->mnt_root == path->dentry; +} + +static void warn_mandlock(void) +{ + pr_warn_once("=======================================================\n" + "WARNING: The mand mount option has been deprecated and\n" + " and is ignored by this kernel. Remove the mand\n" + " option from the mount to silence this warning.\n" + "=======================================================\n"); +} + +static int can_umount(const struct path *path, int flags) +{ + struct mount *mnt = real_mount(path->mnt); + + if (!may_mount()) + return -EPERM; + if (!path_mounted(path)) + return -EINVAL; + if (!check_mnt(mnt)) + return -EINVAL; + if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ + return -EINVAL; + if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) + return -EPERM; + return 0; +} + +// caller is responsible for flags being sane +int path_umount(struct path *path, int flags) +{ + struct mount *mnt = real_mount(path->mnt); + int ret; + + ret = can_umount(path, flags); + if (!ret) + ret = do_umount(mnt, flags); + + /* we mustn't call path_put() as that would clear mnt_expiry_mark */ + dput(path->dentry); + mntput_no_expire(mnt); + return ret; +} + +static int ksys_umount(char __user *name, int flags) +{ + int lookup_flags = LOOKUP_MOUNTPOINT; + struct path path; + int ret; + + // basic validity checks done first + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + + if (!(flags & UMOUNT_NOFOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + ret = user_path_at(AT_FDCWD, name, lookup_flags, &path); + if (ret) + return ret; + return path_umount(&path, flags); +} + +SYSCALL_DEFINE2(umount, char __user *, name, int, flags) +{ + return ksys_umount(name, flags); +} + +#ifdef __ARCH_WANT_SYS_OLDUMOUNT + +/* + * The 2.0 compatible umount. No flags. + */ +SYSCALL_DEFINE1(oldumount, char __user *, name) +{ + return ksys_umount(name, 0); +} + +#endif + +static bool is_mnt_ns_file(struct dentry *dentry) +{ + /* Is this a proxy for a mount namespace? */ + return dentry->d_op == &ns_dentry_operations && + dentry->d_fsdata == &mntns_operations; +} + +static struct mnt_namespace *to_mnt_ns(struct ns_common *ns) +{ + return container_of(ns, struct mnt_namespace, ns); +} + +struct ns_common *from_mnt_ns(struct mnt_namespace *mnt) +{ + return &mnt->ns; +} + +static bool mnt_ns_loop(struct dentry *dentry) +{ + /* Could bind mounting the mount namespace inode cause a + * mount namespace loop? + */ + struct mnt_namespace *mnt_ns; + if (!is_mnt_ns_file(dentry)) + return false; + + mnt_ns = to_mnt_ns(get_proc_ns(dentry->d_inode)); + return current->nsproxy->mnt_ns->seq >= mnt_ns->seq; +} + +struct mount *copy_tree(struct mount *mnt, struct dentry *dentry, + int flag) +{ + struct mount *res, *p, *q, *r, *parent; + + if (!(flag & CL_COPY_UNBINDABLE) && IS_MNT_UNBINDABLE(mnt)) + return ERR_PTR(-EINVAL); + + if (!(flag & CL_COPY_MNT_NS_FILE) && is_mnt_ns_file(dentry)) + return ERR_PTR(-EINVAL); + + res = q = clone_mnt(mnt, dentry, flag); + if (IS_ERR(q)) + return q; + + q->mnt_mountpoint = mnt->mnt_mountpoint; + + p = mnt; + list_for_each_entry(r, &mnt->mnt_mounts, mnt_child) { + struct mount *s; + if (!is_subdir(r->mnt_mountpoint, dentry)) + continue; + + for (s = r; s; s = next_mnt(s, r)) { + if (!(flag & CL_COPY_UNBINDABLE) && + IS_MNT_UNBINDABLE(s)) { + if (s->mnt.mnt_flags & MNT_LOCKED) { + /* Both unbindable and locked. */ + q = ERR_PTR(-EPERM); + goto out; + } else { + s = skip_mnt_tree(s); + continue; + } + } + if (!(flag & CL_COPY_MNT_NS_FILE) && + is_mnt_ns_file(s->mnt.mnt_root)) { + s = skip_mnt_tree(s); + continue; + } + while (p != s->mnt_parent) { + p = p->mnt_parent; + q = q->mnt_parent; + } + p = s; + parent = q; + q = clone_mnt(p, p->mnt.mnt_root, flag); + if (IS_ERR(q)) + goto out; + lock_mount_hash(); + list_add_tail(&q->mnt_list, &res->mnt_list); + attach_mnt(q, parent, p->mnt_mp, false); + unlock_mount_hash(); + } + } + return res; +out: + if (res) { + lock_mount_hash(); + umount_tree(res, UMOUNT_SYNC); + unlock_mount_hash(); + } + return q; +} + +/* Caller should check returned pointer for errors */ + +struct vfsmount *collect_mounts(const struct path *path) +{ + struct mount *tree; + namespace_lock(); + if (!check_mnt(real_mount(path->mnt))) + tree = ERR_PTR(-EINVAL); + else + tree = copy_tree(real_mount(path->mnt), path->dentry, + CL_COPY_ALL | CL_PRIVATE); + namespace_unlock(); + if (IS_ERR(tree)) + return ERR_CAST(tree); + return &tree->mnt; +} + +static void free_mnt_ns(struct mnt_namespace *); +static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *, bool); + +void dissolve_on_fput(struct vfsmount *mnt) +{ + struct mnt_namespace *ns; + namespace_lock(); + lock_mount_hash(); + ns = real_mount(mnt)->mnt_ns; + if (ns) { + if (is_anon_ns(ns)) + umount_tree(real_mount(mnt), UMOUNT_CONNECTED); + else + ns = NULL; + } + unlock_mount_hash(); + namespace_unlock(); + if (ns) + free_mnt_ns(ns); +} + +void drop_collected_mounts(struct vfsmount *mnt) +{ + namespace_lock(); + lock_mount_hash(); + umount_tree(real_mount(mnt), 0); + unlock_mount_hash(); + namespace_unlock(); +} + +static bool has_locked_children(struct mount *mnt, struct dentry *dentry) +{ + struct mount *child; + + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + if (!is_subdir(child->mnt_mountpoint, dentry)) + continue; + + if (child->mnt.mnt_flags & MNT_LOCKED) + return true; + } + return false; +} + +/** + * clone_private_mount - create a private clone of a path + * @path: path to clone + * + * This creates a new vfsmount, which will be the clone of @path. The new mount + * will not be attached anywhere in the namespace and will be private (i.e. + * changes to the originating mount won't be propagated into this). + * + * Release with mntput(). + */ +struct vfsmount *clone_private_mount(const struct path *path) +{ + struct mount *old_mnt = real_mount(path->mnt); + struct mount *new_mnt; + + down_read(&namespace_sem); + if (IS_MNT_UNBINDABLE(old_mnt)) + goto invalid; + + if (!check_mnt(old_mnt)) + goto invalid; + + if (has_locked_children(old_mnt, path->dentry)) + goto invalid; + + new_mnt = clone_mnt(old_mnt, path->dentry, CL_PRIVATE); + up_read(&namespace_sem); + + if (IS_ERR(new_mnt)) + return ERR_CAST(new_mnt); + + /* Longterm mount to be removed by kern_unmount*() */ + new_mnt->mnt_ns = MNT_NS_INTERNAL; + + return &new_mnt->mnt; + +invalid: + up_read(&namespace_sem); + return ERR_PTR(-EINVAL); +} +EXPORT_SYMBOL_GPL(clone_private_mount); + +int iterate_mounts(int (*f)(struct vfsmount *, void *), void *arg, + struct vfsmount *root) +{ + struct mount *mnt; + int res = f(root, arg); + if (res) + return res; + list_for_each_entry(mnt, &real_mount(root)->mnt_list, mnt_list) { + res = f(&mnt->mnt, arg); + if (res) + return res; + } + return 0; +} + +static void lock_mnt_tree(struct mount *mnt) +{ + struct mount *p; + + for (p = mnt; p; p = next_mnt(p, mnt)) { + int flags = p->mnt.mnt_flags; + /* Don't allow unprivileged users to change mount flags */ + flags |= MNT_LOCK_ATIME; + + if (flags & MNT_READONLY) + flags |= MNT_LOCK_READONLY; + + if (flags & MNT_NODEV) + flags |= MNT_LOCK_NODEV; + + if (flags & MNT_NOSUID) + flags |= MNT_LOCK_NOSUID; + + if (flags & MNT_NOEXEC) + flags |= MNT_LOCK_NOEXEC; + /* Don't allow unprivileged users to reveal what is under a mount */ + if (list_empty(&p->mnt_expire)) + flags |= MNT_LOCKED; + p->mnt.mnt_flags = flags; + } +} + +static void cleanup_group_ids(struct mount *mnt, struct mount *end) +{ + struct mount *p; + + for (p = mnt; p != end; p = next_mnt(p, mnt)) { + if (p->mnt_group_id && !IS_MNT_SHARED(p)) + mnt_release_group_id(p); + } +} + +static int invent_group_ids(struct mount *mnt, bool recurse) +{ + struct mount *p; + + for (p = mnt; p; p = recurse ? next_mnt(p, mnt) : NULL) { + if (!p->mnt_group_id && !IS_MNT_SHARED(p)) { + int err = mnt_alloc_group_id(p); + if (err) { + cleanup_group_ids(mnt, p); + return err; + } + } + } + + return 0; +} + +int count_mounts(struct mnt_namespace *ns, struct mount *mnt) +{ + unsigned int max = READ_ONCE(sysctl_mount_max); + unsigned int mounts = 0; + struct mount *p; + + if (ns->mounts >= max) + return -ENOSPC; + max -= ns->mounts; + if (ns->pending_mounts >= max) + return -ENOSPC; + max -= ns->pending_mounts; + + for (p = mnt; p; p = next_mnt(p, mnt)) + mounts++; + + if (mounts > max) + return -ENOSPC; + + ns->pending_mounts += mounts; + return 0; +} + +enum mnt_tree_flags_t { + MNT_TREE_MOVE = BIT(0), + MNT_TREE_BENEATH = BIT(1), +}; + +/** + * attach_recursive_mnt - attach a source mount tree + * @source_mnt: mount tree to be attached + * @top_mnt: mount that @source_mnt will be mounted on or mounted beneath + * @dest_mp: the mountpoint @source_mnt will be mounted at + * @flags: modify how @source_mnt is supposed to be attached + * + * NOTE: in the table below explains the semantics when a source mount + * of a given type is attached to a destination mount of a given type. + * --------------------------------------------------------------------------- + * | BIND MOUNT OPERATION | + * |************************************************************************** + * | source-->| shared | private | slave | unbindable | + * | dest | | | | | + * | | | | | | | + * | v | | | | | + * |************************************************************************** + * | shared | shared (++) | shared (+) | shared(+++)| invalid | + * | | | | | | + * |non-shared| shared (+) | private | slave (*) | invalid | + * *************************************************************************** + * A bind operation clones the source mount and mounts the clone on the + * destination mount. + * + * (++) the cloned mount is propagated to all the mounts in the propagation + * tree of the destination mount and the cloned mount is added to + * the peer group of the source mount. + * (+) the cloned mount is created under the destination mount and is marked + * as shared. The cloned mount is added to the peer group of the source + * mount. + * (+++) the mount is propagated to all the mounts in the propagation tree + * of the destination mount and the cloned mount is made slave + * of the same master as that of the source mount. The cloned mount + * is marked as 'shared and slave'. + * (*) the cloned mount is made a slave of the same master as that of the + * source mount. + * + * --------------------------------------------------------------------------- + * | MOVE MOUNT OPERATION | + * |************************************************************************** + * | source-->| shared | private | slave | unbindable | + * | dest | | | | | + * | | | | | | | + * | v | | | | | + * |************************************************************************** + * | shared | shared (+) | shared (+) | shared(+++) | invalid | + * | | | | | | + * |non-shared| shared (+*) | private | slave (*) | unbindable | + * *************************************************************************** + * + * (+) the mount is moved to the destination. And is then propagated to + * all the mounts in the propagation tree of the destination mount. + * (+*) the mount is moved to the destination. + * (+++) the mount is moved to the destination and is then propagated to + * all the mounts belonging to the destination mount's propagation tree. + * the mount is marked as 'shared and slave'. + * (*) the mount continues to be a slave at the new location. + * + * if the source mount is a tree, the operations explained above is + * applied to each mount in the tree. + * Must be called without spinlocks held, since this function can sleep + * in allocations. + * + * Context: The function expects namespace_lock() to be held. + * Return: If @source_mnt was successfully attached 0 is returned. + * Otherwise a negative error code is returned. + */ +static int attach_recursive_mnt(struct mount *source_mnt, + struct mount *top_mnt, + struct mountpoint *dest_mp, + enum mnt_tree_flags_t flags) +{ + struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; + HLIST_HEAD(tree_list); + struct mnt_namespace *ns = top_mnt->mnt_ns; + struct mountpoint *smp; + struct mount *child, *dest_mnt, *p; + struct hlist_node *n; + int err = 0; + bool moving = flags & MNT_TREE_MOVE, beneath = flags & MNT_TREE_BENEATH; + + /* + * Preallocate a mountpoint in case the new mounts need to be + * mounted beneath mounts on the same mountpoint. + */ + smp = get_mountpoint(source_mnt->mnt.mnt_root); + if (IS_ERR(smp)) + return PTR_ERR(smp); + + /* Is there space to add these mounts to the mount namespace? */ + if (!moving) { + err = count_mounts(ns, source_mnt); + if (err) + goto out; + } + + if (beneath) + dest_mnt = top_mnt->mnt_parent; + else + dest_mnt = top_mnt; + + if (IS_MNT_SHARED(dest_mnt)) { + err = invent_group_ids(source_mnt, true); + if (err) + goto out; + err = propagate_mnt(dest_mnt, dest_mp, source_mnt, &tree_list); + } + lock_mount_hash(); + if (err) + goto out_cleanup_ids; + + if (IS_MNT_SHARED(dest_mnt)) { + for (p = source_mnt; p; p = next_mnt(p, source_mnt)) + set_mnt_shared(p); + } + + if (moving) { + if (beneath) + dest_mp = smp; + unhash_mnt(source_mnt); + attach_mnt(source_mnt, top_mnt, dest_mp, beneath); + touch_mnt_namespace(source_mnt->mnt_ns); + } else { + if (source_mnt->mnt_ns) { + /* move from anon - the caller will destroy */ + list_del_init(&source_mnt->mnt_ns->list); + } + if (beneath) + mnt_set_mountpoint_beneath(source_mnt, top_mnt, smp); + else + mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt); + commit_tree(source_mnt); + } + + hlist_for_each_entry_safe(child, n, &tree_list, mnt_hash) { + struct mount *q; + hlist_del_init(&child->mnt_hash); + q = __lookup_mnt(&child->mnt_parent->mnt, + child->mnt_mountpoint); + if (q) + mnt_change_mountpoint(child, smp, q); + /* Notice when we are propagating across user namespaces */ + if (child->mnt_parent->mnt_ns->user_ns != user_ns) + lock_mnt_tree(child); + child->mnt.mnt_flags &= ~MNT_LOCKED; + commit_tree(child); + } + put_mountpoint(smp); + unlock_mount_hash(); + + return 0; + + out_cleanup_ids: + while (!hlist_empty(&tree_list)) { + child = hlist_entry(tree_list.first, struct mount, mnt_hash); + child->mnt_parent->mnt_ns->pending_mounts = 0; + umount_tree(child, UMOUNT_SYNC); + } + unlock_mount_hash(); + cleanup_group_ids(source_mnt, NULL); + out: + ns->pending_mounts = 0; + + read_seqlock_excl(&mount_lock); + put_mountpoint(smp); + read_sequnlock_excl(&mount_lock); + + return err; +} + +/** + * do_lock_mount - lock mount and mountpoint + * @path: target path + * @beneath: whether the intention is to mount beneath @path + * + * Follow the mount stack on @path until the top mount @mnt is found. If + * the initial @path->{mnt,dentry} is a mountpoint lookup the first + * mount stacked on top of it. Then simply follow @{mnt,mnt->mnt_root} + * until nothing is stacked on top of it anymore. + * + * Acquire the inode_lock() on the top mount's ->mnt_root to protect + * against concurrent removal of the new mountpoint from another mount + * namespace. + * + * If @beneath is requested, acquire inode_lock() on @mnt's mountpoint + * @mp on @mnt->mnt_parent must be acquired. This protects against a + * concurrent unlink of @mp->mnt_dentry from another mount namespace + * where @mnt doesn't have a child mount mounted @mp. A concurrent + * removal of @mnt->mnt_root doesn't matter as nothing will be mounted + * on top of it for @beneath. + * + * In addition, @beneath needs to make sure that @mnt hasn't been + * unmounted or moved from its current mountpoint in between dropping + * @mount_lock and acquiring @namespace_sem. For the !@beneath case @mnt + * being unmounted would be detected later by e.g., calling + * check_mnt(mnt) in the function it's called from. For the @beneath + * case however, it's useful to detect it directly in do_lock_mount(). + * If @mnt hasn't been unmounted then @mnt->mnt_mountpoint still points + * to @mnt->mnt_mp->m_dentry. But if @mnt has been unmounted it will + * point to @mnt->mnt_root and @mnt->mnt_mp will be NULL. + * + * Return: Either the target mountpoint on the top mount or the top + * mount's mountpoint. + */ +static struct mountpoint *do_lock_mount(struct path *path, bool beneath) +{ + struct vfsmount *mnt = path->mnt; + struct dentry *dentry; + struct mountpoint *mp = ERR_PTR(-ENOENT); + + for (;;) { + struct mount *m; + + if (beneath) { + m = real_mount(mnt); + read_seqlock_excl(&mount_lock); + dentry = dget(m->mnt_mountpoint); + read_sequnlock_excl(&mount_lock); + } else { + dentry = path->dentry; + } + + inode_lock(dentry->d_inode); + if (unlikely(cant_mount(dentry))) { + inode_unlock(dentry->d_inode); + goto out; + } + + namespace_lock(); + + if (beneath && (!is_mounted(mnt) || m->mnt_mountpoint != dentry)) { + namespace_unlock(); + inode_unlock(dentry->d_inode); + goto out; + } + + mnt = lookup_mnt(path); + if (likely(!mnt)) + break; + + namespace_unlock(); + inode_unlock(dentry->d_inode); + if (beneath) + dput(dentry); + path_put(path); + path->mnt = mnt; + path->dentry = dget(mnt->mnt_root); + } + + mp = get_mountpoint(dentry); + if (IS_ERR(mp)) { + namespace_unlock(); + inode_unlock(dentry->d_inode); + } + +out: + if (beneath) + dput(dentry); + + return mp; +} + +static inline struct mountpoint *lock_mount(struct path *path) +{ + return do_lock_mount(path, false); +} + +static void unlock_mount(struct mountpoint *where) +{ + struct dentry *dentry = where->m_dentry; + + read_seqlock_excl(&mount_lock); + put_mountpoint(where); + read_sequnlock_excl(&mount_lock); + + namespace_unlock(); + inode_unlock(dentry->d_inode); +} + +static int graft_tree(struct mount *mnt, struct mount *p, struct mountpoint *mp) +{ + if (mnt->mnt.mnt_sb->s_flags & SB_NOUSER) + return -EINVAL; + + if (d_is_dir(mp->m_dentry) != + d_is_dir(mnt->mnt.mnt_root)) + return -ENOTDIR; + + return attach_recursive_mnt(mnt, p, mp, 0); +} + +/* + * Sanity check the flags to change_mnt_propagation. + */ + +static int flags_to_propagation_type(int ms_flags) +{ + int type = ms_flags & ~(MS_REC | MS_SILENT); + + /* Fail if any non-propagation flags are set */ + if (type & ~(MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + return 0; + /* Only one propagation flag should be set */ + if (!is_power_of_2(type)) + return 0; + return type; +} + +/* + * recursively change the type of the mountpoint. + */ +static int do_change_type(struct path *path, int ms_flags) +{ + struct mount *m; + struct mount *mnt = real_mount(path->mnt); + int recurse = ms_flags & MS_REC; + int type; + int err = 0; + + if (!path_mounted(path)) + return -EINVAL; + + type = flags_to_propagation_type(ms_flags); + if (!type) + return -EINVAL; + + namespace_lock(); + if (type == MS_SHARED) { + err = invent_group_ids(mnt, recurse); + if (err) + goto out_unlock; + } + + lock_mount_hash(); + for (m = mnt; m; m = (recurse ? next_mnt(m, mnt) : NULL)) + change_mnt_propagation(m, type); + unlock_mount_hash(); + + out_unlock: + namespace_unlock(); + return err; +} + +static struct mount *__do_loopback(struct path *old_path, int recurse) +{ + struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt); + + if (IS_MNT_UNBINDABLE(old)) + return mnt; + + if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations) + return mnt; + + if (!recurse && has_locked_children(old, old_path->dentry)) + return mnt; + + if (recurse) + mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE); + else + mnt = clone_mnt(old, old_path->dentry, 0); + + if (!IS_ERR(mnt)) + mnt->mnt.mnt_flags &= ~MNT_LOCKED; + + return mnt; +} + +/* + * do loopback mount. + */ +static int do_loopback(struct path *path, const char *old_name, + int recurse) +{ + struct path old_path; + struct mount *mnt = NULL, *parent; + struct mountpoint *mp; + int err; + if (!old_name || !*old_name) + return -EINVAL; + err = kern_path(old_name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &old_path); + if (err) + return err; + + err = -EINVAL; + if (mnt_ns_loop(old_path.dentry)) + goto out; + + mp = lock_mount(path); + if (IS_ERR(mp)) { + err = PTR_ERR(mp); + goto out; + } + + parent = real_mount(path->mnt); + if (!check_mnt(parent)) + goto out2; + + mnt = __do_loopback(&old_path, recurse); + if (IS_ERR(mnt)) { + err = PTR_ERR(mnt); + goto out2; + } + + err = graft_tree(mnt, parent, mp); + if (err) { + lock_mount_hash(); + umount_tree(mnt, UMOUNT_SYNC); + unlock_mount_hash(); + } +out2: + unlock_mount(mp); +out: + path_put(&old_path); + return err; +} + +static struct file *open_detached_copy(struct path *path, bool recursive) +{ + struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns; + struct mnt_namespace *ns = alloc_mnt_ns(user_ns, true); + struct mount *mnt, *p; + struct file *file; + + if (IS_ERR(ns)) + return ERR_CAST(ns); + + namespace_lock(); + mnt = __do_loopback(path, recursive); + if (IS_ERR(mnt)) { + namespace_unlock(); + free_mnt_ns(ns); + return ERR_CAST(mnt); + } + + lock_mount_hash(); + for (p = mnt; p; p = next_mnt(p, mnt)) { + p->mnt_ns = ns; + ns->mounts++; + } + ns->root = mnt; + list_add_tail(&ns->list, &mnt->mnt_list); + mntget(&mnt->mnt); + unlock_mount_hash(); + namespace_unlock(); + + mntput(path->mnt); + path->mnt = &mnt->mnt; + file = dentry_open(path, O_PATH, current_cred()); + if (IS_ERR(file)) + dissolve_on_fput(path->mnt); + else + file->f_mode |= FMODE_NEED_UNMOUNT; + return file; +} + +SYSCALL_DEFINE3(open_tree, int, dfd, const char __user *, filename, unsigned, flags) +{ + struct file *file; + struct path path; + int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; + bool detached = flags & OPEN_TREE_CLONE; + int error; + int fd; + + BUILD_BUG_ON(OPEN_TREE_CLOEXEC != O_CLOEXEC); + + if (flags & ~(AT_EMPTY_PATH | AT_NO_AUTOMOUNT | AT_RECURSIVE | + AT_SYMLINK_NOFOLLOW | OPEN_TREE_CLONE | + OPEN_TREE_CLOEXEC)) + return -EINVAL; + + if ((flags & (AT_RECURSIVE | OPEN_TREE_CLONE)) == AT_RECURSIVE) + return -EINVAL; + + if (flags & AT_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (flags & AT_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + if (flags & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; + + if (detached && !may_mount()) + return -EPERM; + + fd = get_unused_fd_flags(flags & O_CLOEXEC); + if (fd < 0) + return fd; + + error = user_path_at(dfd, filename, lookup_flags, &path); + if (unlikely(error)) { + file = ERR_PTR(error); + } else { + if (detached) + file = open_detached_copy(&path, flags & AT_RECURSIVE); + else + file = dentry_open(&path, O_PATH, current_cred()); + path_put(&path); + } + if (IS_ERR(file)) { + put_unused_fd(fd); + return PTR_ERR(file); + } + fd_install(fd, file); + return fd; +} + +/* + * Don't allow locked mount flags to be cleared. + * + * No locks need to be held here while testing the various MNT_LOCK + * flags because those flags can never be cleared once they are set. + */ +static bool can_change_locked_flags(struct mount *mnt, unsigned int mnt_flags) +{ + unsigned int fl = mnt->mnt.mnt_flags; + + if ((fl & MNT_LOCK_READONLY) && + !(mnt_flags & MNT_READONLY)) + return false; + + if ((fl & MNT_LOCK_NODEV) && + !(mnt_flags & MNT_NODEV)) + return false; + + if ((fl & MNT_LOCK_NOSUID) && + !(mnt_flags & MNT_NOSUID)) + return false; + + if ((fl & MNT_LOCK_NOEXEC) && + !(mnt_flags & MNT_NOEXEC)) + return false; + + if ((fl & MNT_LOCK_ATIME) && + ((fl & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) + return false; + + return true; +} + +static int change_mount_ro_state(struct mount *mnt, unsigned int mnt_flags) +{ + bool readonly_request = (mnt_flags & MNT_READONLY); + + if (readonly_request == __mnt_is_readonly(&mnt->mnt)) + return 0; + + if (readonly_request) + return mnt_make_readonly(mnt); + + mnt->mnt.mnt_flags &= ~MNT_READONLY; + return 0; +} + +static void set_mount_attributes(struct mount *mnt, unsigned int mnt_flags) +{ + mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; + mnt->mnt.mnt_flags = mnt_flags; + touch_mnt_namespace(mnt->mnt_ns); +} + +static void mnt_warn_timestamp_expiry(struct path *mountpoint, struct vfsmount *mnt) +{ + struct super_block *sb = mnt->mnt_sb; + + if (!__mnt_is_readonly(mnt) && + (!(sb->s_iflags & SB_I_TS_EXPIRY_WARNED)) && + (ktime_get_real_seconds() + TIME_UPTIME_SEC_MAX > sb->s_time_max)) { + char *buf = (char *)__get_free_page(GFP_KERNEL); + char *mntpath = buf ? d_path(mountpoint, buf, PAGE_SIZE) : ERR_PTR(-ENOMEM); + + pr_warn("%s filesystem being %s at %s supports timestamps until %ptTd (0x%llx)\n", + sb->s_type->name, + is_mounted(mnt) ? "remounted" : "mounted", + mntpath, &sb->s_time_max, + (unsigned long long)sb->s_time_max); + + free_page((unsigned long)buf); + sb->s_iflags |= SB_I_TS_EXPIRY_WARNED; + } +} + +/* + * Handle reconfiguration of the mountpoint only without alteration of the + * superblock it refers to. This is triggered by specifying MS_REMOUNT|MS_BIND + * to mount(2). + */ +static int do_reconfigure_mnt(struct path *path, unsigned int mnt_flags) +{ + struct super_block *sb = path->mnt->mnt_sb; + struct mount *mnt = real_mount(path->mnt); + int ret; + + if (!check_mnt(mnt)) + return -EINVAL; + + if (!path_mounted(path)) + return -EINVAL; + + if (!can_change_locked_flags(mnt, mnt_flags)) + return -EPERM; + + /* + * We're only checking whether the superblock is read-only not + * changing it, so only take down_read(&sb->s_umount). + */ + down_read(&sb->s_umount); + lock_mount_hash(); + ret = change_mount_ro_state(mnt, mnt_flags); + if (ret == 0) + set_mount_attributes(mnt, mnt_flags); + unlock_mount_hash(); + up_read(&sb->s_umount); + + mnt_warn_timestamp_expiry(path, &mnt->mnt); + + return ret; +} + +/* + * change filesystem flags. dir should be a physical root of filesystem. + * If you've mounted a non-root directory somewhere and want to do remount + * on it - tough luck. + */ +static int do_remount(struct path *path, int ms_flags, int sb_flags, + int mnt_flags, void *data) +{ + int err; + struct super_block *sb = path->mnt->mnt_sb; + struct mount *mnt = real_mount(path->mnt); + struct fs_context *fc; + + if (!check_mnt(mnt)) + return -EINVAL; + + if (!path_mounted(path)) + return -EINVAL; + + if (!can_change_locked_flags(mnt, mnt_flags)) + return -EPERM; + + fc = fs_context_for_reconfigure(path->dentry, sb_flags, MS_RMT_MASK); + if (IS_ERR(fc)) + return PTR_ERR(fc); + + /* + * Indicate to the filesystem that the remount request is coming + * from the legacy mount system call. + */ + fc->oldapi = true; + + err = parse_monolithic_mount_data(fc, data); + if (!err) { + down_write(&sb->s_umount); + err = -EPERM; + if (ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) { + err = reconfigure_super(fc); + if (!err) { + lock_mount_hash(); + set_mount_attributes(mnt, mnt_flags); + unlock_mount_hash(); + } + } + up_write(&sb->s_umount); + } + + mnt_warn_timestamp_expiry(path, &mnt->mnt); + + put_fs_context(fc); + return err; +} + +static inline int tree_contains_unbindable(struct mount *mnt) +{ + struct mount *p; + for (p = mnt; p; p = next_mnt(p, mnt)) { + if (IS_MNT_UNBINDABLE(p)) + return 1; + } + return 0; +} + +/* + * Check that there aren't references to earlier/same mount namespaces in the + * specified subtree. Such references can act as pins for mount namespaces + * that aren't checked by the mount-cycle checking code, thereby allowing + * cycles to be made. + */ +static bool check_for_nsfs_mounts(struct mount *subtree) +{ + struct mount *p; + bool ret = false; + + lock_mount_hash(); + for (p = subtree; p; p = next_mnt(p, subtree)) + if (mnt_ns_loop(p->mnt.mnt_root)) + goto out; + + ret = true; +out: + unlock_mount_hash(); + return ret; +} + +static int do_set_group(struct path *from_path, struct path *to_path) +{ + struct mount *from, *to; + int err; + + from = real_mount(from_path->mnt); + to = real_mount(to_path->mnt); + + namespace_lock(); + + err = -EINVAL; + /* To and From must be mounted */ + if (!is_mounted(&from->mnt)) + goto out; + if (!is_mounted(&to->mnt)) + goto out; + + err = -EPERM; + /* We should be allowed to modify mount namespaces of both mounts */ + if (!ns_capable(from->mnt_ns->user_ns, CAP_SYS_ADMIN)) + goto out; + if (!ns_capable(to->mnt_ns->user_ns, CAP_SYS_ADMIN)) + goto out; + + err = -EINVAL; + /* To and From paths should be mount roots */ + if (!path_mounted(from_path)) + goto out; + if (!path_mounted(to_path)) + goto out; + + /* Setting sharing groups is only allowed across same superblock */ + if (from->mnt.mnt_sb != to->mnt.mnt_sb) + goto out; + + /* From mount root should be wider than To mount root */ + if (!is_subdir(to->mnt.mnt_root, from->mnt.mnt_root)) + goto out; + + /* From mount should not have locked children in place of To's root */ + if (has_locked_children(from, to->mnt.mnt_root)) + goto out; + + /* Setting sharing groups is only allowed on private mounts */ + if (IS_MNT_SHARED(to) || IS_MNT_SLAVE(to)) + goto out; + + /* From should not be private */ + if (!IS_MNT_SHARED(from) && !IS_MNT_SLAVE(from)) + goto out; + + if (IS_MNT_SLAVE(from)) { + struct mount *m = from->mnt_master; + + list_add(&to->mnt_slave, &m->mnt_slave_list); + to->mnt_master = m; + } + + if (IS_MNT_SHARED(from)) { + to->mnt_group_id = from->mnt_group_id; + list_add(&to->mnt_share, &from->mnt_share); + lock_mount_hash(); + set_mnt_shared(to); + unlock_mount_hash(); + } + + err = 0; +out: + namespace_unlock(); + return err; +} + +/** + * path_overmounted - check if path is overmounted + * @path: path to check + * + * Check if path is overmounted, i.e., if there's a mount on top of + * @path->mnt with @path->dentry as mountpoint. + * + * Context: This function expects namespace_lock() to be held. + * Return: If path is overmounted true is returned, false if not. + */ +static inline bool path_overmounted(const struct path *path) +{ + rcu_read_lock(); + if (unlikely(__lookup_mnt(path->mnt, path->dentry))) { + rcu_read_unlock(); + return true; + } + rcu_read_unlock(); + return false; +} + +/** + * can_move_mount_beneath - check that we can mount beneath the top mount + * @from: mount to mount beneath + * @to: mount under which to mount + * + * - Make sure that @to->dentry is actually the root of a mount under + * which we can mount another mount. + * - Make sure that nothing can be mounted beneath the caller's current + * root or the rootfs of the namespace. + * - Make sure that the caller can unmount the topmost mount ensuring + * that the caller could reveal the underlying mountpoint. + * - Ensure that nothing has been mounted on top of @from before we + * grabbed @namespace_sem to avoid creating pointless shadow mounts. + * - Prevent mounting beneath a mount if the propagation relationship + * between the source mount, parent mount, and top mount would lead to + * nonsensical mount trees. + * + * Context: This function expects namespace_lock() to be held. + * Return: On success 0, and on error a negative error code is returned. + */ +static int can_move_mount_beneath(const struct path *from, + const struct path *to, + const struct mountpoint *mp) +{ + struct mount *mnt_from = real_mount(from->mnt), + *mnt_to = real_mount(to->mnt), + *parent_mnt_to = mnt_to->mnt_parent; + + if (!mnt_has_parent(mnt_to)) + return -EINVAL; + + if (!path_mounted(to)) + return -EINVAL; + + if (IS_MNT_LOCKED(mnt_to)) + return -EINVAL; + + /* Avoid creating shadow mounts during mount propagation. */ + if (path_overmounted(from)) + return -EINVAL; + + /* + * Mounting beneath the rootfs only makes sense when the + * semantics of pivot_root(".", ".") are used. + */ + if (&mnt_to->mnt == current->fs->root.mnt) + return -EINVAL; + if (parent_mnt_to == current->nsproxy->mnt_ns->root) + return -EINVAL; + + for (struct mount *p = mnt_from; mnt_has_parent(p); p = p->mnt_parent) + if (p == mnt_to) + return -EINVAL; + + /* + * If the parent mount propagates to the child mount this would + * mean mounting @mnt_from on @mnt_to->mnt_parent and then + * propagating a copy @c of @mnt_from on top of @mnt_to. This + * defeats the whole purpose of mounting beneath another mount. + */ + if (propagation_would_overmount(parent_mnt_to, mnt_to, mp)) + return -EINVAL; + + /* + * If @mnt_to->mnt_parent propagates to @mnt_from this would + * mean propagating a copy @c of @mnt_from on top of @mnt_from. + * Afterwards @mnt_from would be mounted on top of + * @mnt_to->mnt_parent and @mnt_to would be unmounted from + * @mnt->mnt_parent and remounted on @mnt_from. But since @c is + * already mounted on @mnt_from, @mnt_to would ultimately be + * remounted on top of @c. Afterwards, @mnt_from would be + * covered by a copy @c of @mnt_from and @c would be covered by + * @mnt_from itself. This defeats the whole purpose of mounting + * @mnt_from beneath @mnt_to. + */ + if (propagation_would_overmount(parent_mnt_to, mnt_from, mp)) + return -EINVAL; + + return 0; +} + +static int do_move_mount(struct path *old_path, struct path *new_path, + bool beneath) +{ + struct mnt_namespace *ns; + struct mount *p; + struct mount *old; + struct mount *parent; + struct mountpoint *mp, *old_mp; + int err; + bool attached; + enum mnt_tree_flags_t flags = 0; + + mp = do_lock_mount(new_path, beneath); + if (IS_ERR(mp)) + return PTR_ERR(mp); + + old = real_mount(old_path->mnt); + p = real_mount(new_path->mnt); + parent = old->mnt_parent; + attached = mnt_has_parent(old); + if (attached) + flags |= MNT_TREE_MOVE; + old_mp = old->mnt_mp; + ns = old->mnt_ns; + + err = -EINVAL; + /* The mountpoint must be in our namespace. */ + if (!check_mnt(p)) + goto out; + + /* The thing moved must be mounted... */ + if (!is_mounted(&old->mnt)) + goto out; + + /* ... and either ours or the root of anon namespace */ + if (!(attached ? check_mnt(old) : is_anon_ns(ns))) + goto out; + + if (old->mnt.mnt_flags & MNT_LOCKED) + goto out; + + if (!path_mounted(old_path)) + goto out; + + if (d_is_dir(new_path->dentry) != + d_is_dir(old_path->dentry)) + goto out; + /* + * Don't move a mount residing in a shared parent. + */ + if (attached && IS_MNT_SHARED(parent)) + goto out; + + if (beneath) { + err = can_move_mount_beneath(old_path, new_path, mp); + if (err) + goto out; + + err = -EINVAL; + p = p->mnt_parent; + flags |= MNT_TREE_BENEATH; + } + + /* + * Don't move a mount tree containing unbindable mounts to a destination + * mount which is shared. + */ + if (IS_MNT_SHARED(p) && tree_contains_unbindable(old)) + goto out; + err = -ELOOP; + if (!check_for_nsfs_mounts(old)) + goto out; + for (; mnt_has_parent(p); p = p->mnt_parent) + if (p == old) + goto out; + + err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, flags); + if (err) + goto out; + + /* if the mount is moved, it should no longer be expire + * automatically */ + list_del_init(&old->mnt_expire); + if (attached) + put_mountpoint(old_mp); +out: + unlock_mount(mp); + if (!err) { + if (attached) + mntput_no_expire(parent); + else + free_mnt_ns(ns); + } + return err; +} + +static int do_move_mount_old(struct path *path, const char *old_name) +{ + struct path old_path; + int err; + + if (!old_name || !*old_name) + return -EINVAL; + + err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); + if (err) + return err; + + err = do_move_mount(&old_path, path, false); + path_put(&old_path); + return err; +} + +/* + * add a mount into a namespace's mount tree + */ +static int do_add_mount(struct mount *newmnt, struct mountpoint *mp, + const struct path *path, int mnt_flags) +{ + struct mount *parent = real_mount(path->mnt); + + mnt_flags &= ~MNT_INTERNAL_FLAGS; + + if (unlikely(!check_mnt(parent))) { + /* that's acceptable only for automounts done in private ns */ + if (!(mnt_flags & MNT_SHRINKABLE)) + return -EINVAL; + /* ... and for those we'd better have mountpoint still alive */ + if (!parent->mnt_ns) + return -EINVAL; + } + + /* Refuse the same filesystem on the same mount point */ + if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && path_mounted(path)) + return -EBUSY; + + if (d_is_symlink(newmnt->mnt.mnt_root)) + return -EINVAL; + + newmnt->mnt.mnt_flags = mnt_flags; + return graft_tree(newmnt, parent, mp); +} + +static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags); + +/* + * Create a new mount using a superblock configuration and request it + * be added to the namespace tree. + */ +static int do_new_mount_fc(struct fs_context *fc, struct path *mountpoint, + unsigned int mnt_flags) +{ + struct vfsmount *mnt; + struct mountpoint *mp; + struct super_block *sb = fc->root->d_sb; + int error; + + error = security_sb_kern_mount(sb); + if (!error && mount_too_revealing(sb, &mnt_flags)) + error = -EPERM; + + if (unlikely(error)) { + fc_drop_locked(fc); + return error; + } + + up_write(&sb->s_umount); + + mnt = vfs_create_mount(fc); + if (IS_ERR(mnt)) + return PTR_ERR(mnt); + + mnt_warn_timestamp_expiry(mountpoint, mnt); + + mp = lock_mount(mountpoint); + if (IS_ERR(mp)) { + mntput(mnt); + return PTR_ERR(mp); + } + error = do_add_mount(real_mount(mnt), mp, mountpoint, mnt_flags); + unlock_mount(mp); + if (error < 0) + mntput(mnt); + return error; +} + +/* + * create a new mount for userspace and request it to be added into the + * namespace's tree + */ +static int do_new_mount(struct path *path, const char *fstype, int sb_flags, + int mnt_flags, const char *name, void *data) +{ + struct file_system_type *type; + struct fs_context *fc; + const char *subtype = NULL; + int err = 0; + + if (!fstype) + return -EINVAL; + + type = get_fs_type(fstype); + if (!type) + return -ENODEV; + + if (type->fs_flags & FS_HAS_SUBTYPE) { + subtype = strchr(fstype, '.'); + if (subtype) { + subtype++; + if (!*subtype) { + put_filesystem(type); + return -EINVAL; + } + } + } + + fc = fs_context_for_mount(type, sb_flags); + put_filesystem(type); + if (IS_ERR(fc)) + return PTR_ERR(fc); + + /* + * Indicate to the filesystem that the mount request is coming + * from the legacy mount system call. + */ + fc->oldapi = true; + + if (subtype) + err = vfs_parse_fs_string(fc, "subtype", + subtype, strlen(subtype)); + if (!err && name) + err = vfs_parse_fs_string(fc, "source", name, strlen(name)); + if (!err) + err = parse_monolithic_mount_data(fc, data); + if (!err && !mount_capable(fc)) + err = -EPERM; + if (!err) + err = vfs_get_tree(fc); + if (!err) + err = do_new_mount_fc(fc, path, mnt_flags); + + put_fs_context(fc); + return err; +} + +int finish_automount(struct vfsmount *m, const struct path *path) +{ + struct dentry *dentry = path->dentry; + struct mountpoint *mp; + struct mount *mnt; + int err; + + if (!m) + return 0; + if (IS_ERR(m)) + return PTR_ERR(m); + + mnt = real_mount(m); + /* The new mount record should have at least 2 refs to prevent it being + * expired before we get a chance to add it + */ + BUG_ON(mnt_get_count(mnt) < 2); + + if (m->mnt_sb == path->mnt->mnt_sb && + m->mnt_root == dentry) { + err = -ELOOP; + goto discard; + } + + /* + * we don't want to use lock_mount() - in this case finding something + * that overmounts our mountpoint to be means "quitely drop what we've + * got", not "try to mount it on top". + */ + inode_lock(dentry->d_inode); + namespace_lock(); + if (unlikely(cant_mount(dentry))) { + err = -ENOENT; + goto discard_locked; + } + if (path_overmounted(path)) { + err = 0; + goto discard_locked; + } + mp = get_mountpoint(dentry); + if (IS_ERR(mp)) { + err = PTR_ERR(mp); + goto discard_locked; + } + + err = do_add_mount(mnt, mp, path, path->mnt->mnt_flags | MNT_SHRINKABLE); + unlock_mount(mp); + if (unlikely(err)) + goto discard; + mntput(m); + return 0; + +discard_locked: + namespace_unlock(); + inode_unlock(dentry->d_inode); +discard: + /* remove m from any expiration list it may be on */ + if (!list_empty(&mnt->mnt_expire)) { + namespace_lock(); + list_del_init(&mnt->mnt_expire); + namespace_unlock(); + } + mntput(m); + mntput(m); + return err; +} + +/** + * mnt_set_expiry - Put a mount on an expiration list + * @mnt: The mount to list. + * @expiry_list: The list to add the mount to. + */ +void mnt_set_expiry(struct vfsmount *mnt, struct list_head *expiry_list) +{ + namespace_lock(); + + list_add_tail(&real_mount(mnt)->mnt_expire, expiry_list); + + namespace_unlock(); +} +EXPORT_SYMBOL(mnt_set_expiry); + +/* + * process a list of expirable mountpoints with the intent of discarding any + * mountpoints that aren't in use and haven't been touched since last we came + * here + */ +void mark_mounts_for_expiry(struct list_head *mounts) +{ + struct mount *mnt, *next; + LIST_HEAD(graveyard); + + if (list_empty(mounts)) + return; + + namespace_lock(); + lock_mount_hash(); + + /* extract from the expiration list every vfsmount that matches the + * following criteria: + * - only referenced by its parent vfsmount + * - still marked for expiry (marked on the last call here; marks are + * cleared by mntput()) + */ + list_for_each_entry_safe(mnt, next, mounts, mnt_expire) { + if (!xchg(&mnt->mnt_expiry_mark, 1) || + propagate_mount_busy(mnt, 1)) + continue; + list_move(&mnt->mnt_expire, &graveyard); + } + while (!list_empty(&graveyard)) { + mnt = list_first_entry(&graveyard, struct mount, mnt_expire); + touch_mnt_namespace(mnt->mnt_ns); + umount_tree(mnt, UMOUNT_PROPAGATE|UMOUNT_SYNC); + } + unlock_mount_hash(); + namespace_unlock(); +} + +EXPORT_SYMBOL_GPL(mark_mounts_for_expiry); + +/* + * Ripoff of 'select_parent()' + * + * search the list of submounts for a given mountpoint, and move any + * shrinkable submounts to the 'graveyard' list. + */ +static int select_submounts(struct mount *parent, struct list_head *graveyard) +{ + struct mount *this_parent = parent; + struct list_head *next; + int found = 0; + +repeat: + next = this_parent->mnt_mounts.next; +resume: + while (next != &this_parent->mnt_mounts) { + struct list_head *tmp = next; + struct mount *mnt = list_entry(tmp, struct mount, mnt_child); + + next = tmp->next; + if (!(mnt->mnt.mnt_flags & MNT_SHRINKABLE)) + continue; + /* + * Descend a level if the d_mounts list is non-empty. + */ + if (!list_empty(&mnt->mnt_mounts)) { + this_parent = mnt; + goto repeat; + } + + if (!propagate_mount_busy(mnt, 1)) { + list_move_tail(&mnt->mnt_expire, graveyard); + found++; + } + } + /* + * All done at this level ... ascend and resume the search + */ + if (this_parent != parent) { + next = this_parent->mnt_child.next; + this_parent = this_parent->mnt_parent; + goto resume; + } + return found; +} + +/* + * process a list of expirable mountpoints with the intent of discarding any + * submounts of a specific parent mountpoint + * + * mount_lock must be held for write + */ +static void shrink_submounts(struct mount *mnt) +{ + LIST_HEAD(graveyard); + struct mount *m; + + /* extract submounts of 'mountpoint' from the expiration list */ + while (select_submounts(mnt, &graveyard)) { + while (!list_empty(&graveyard)) { + m = list_first_entry(&graveyard, struct mount, + mnt_expire); + touch_mnt_namespace(m->mnt_ns); + umount_tree(m, UMOUNT_PROPAGATE|UMOUNT_SYNC); + } + } +} + +static void *copy_mount_options(const void __user * data) +{ + char *copy; + unsigned left, offset; + + if (!data) + return NULL; + + copy = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!copy) + return ERR_PTR(-ENOMEM); + + left = copy_from_user(copy, data, PAGE_SIZE); + + /* + * Not all architectures have an exact copy_from_user(). Resort to + * byte at a time. + */ + offset = PAGE_SIZE - left; + while (left) { + char c; + if (get_user(c, (const char __user *)data + offset)) + break; + copy[offset] = c; + left--; + offset++; + } + + if (left == PAGE_SIZE) { + kfree(copy); + return ERR_PTR(-EFAULT); + } + + return copy; +} + +static char *copy_mount_string(const void __user *data) +{ + return data ? strndup_user(data, PATH_MAX) : NULL; +} + +/* + * Flags is a 32-bit value that allows up to 31 non-fs dependent flags to + * be given to the mount() call (ie: read-only, no-dev, no-suid etc). + * + * data is a (void *) that can point to any structure up to + * PAGE_SIZE-1 bytes, which can contain arbitrary fs-dependent + * information (or be NULL). + * + * Pre-0.97 versions of mount() didn't have a flags word. + * When the flags word was introduced its top half was required + * to have the magic value 0xC0ED, and this remained so until 2.4.0-test9. + * Therefore, if this magic number is present, it carries no information + * and must be discarded. + */ +int path_mount(const char *dev_name, struct path *path, + const char *type_page, unsigned long flags, void *data_page) +{ + unsigned int mnt_flags = 0, sb_flags; + int ret; + + /* Discard magic */ + if ((flags & MS_MGC_MSK) == MS_MGC_VAL) + flags &= ~MS_MGC_MSK; + + /* Basic sanity checks */ + if (data_page) + ((char *)data_page)[PAGE_SIZE - 1] = 0; + + if (flags & MS_NOUSER) + return -EINVAL; + + ret = security_sb_mount(dev_name, path, type_page, flags, data_page); + if (ret) + return ret; + if (!may_mount()) + return -EPERM; + if (flags & SB_MANDLOCK) + warn_mandlock(); + + /* Default to relatime unless overriden */ + if (!(flags & MS_NOATIME)) + mnt_flags |= MNT_RELATIME; + + /* Separate the per-mountpoint flags */ + if (flags & MS_NOSUID) + mnt_flags |= MNT_NOSUID; + if (flags & MS_NODEV) + mnt_flags |= MNT_NODEV; + if (flags & MS_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (flags & MS_NOATIME) + mnt_flags |= MNT_NOATIME; + if (flags & MS_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + if (flags & MS_STRICTATIME) + mnt_flags &= ~(MNT_RELATIME | MNT_NOATIME); + if (flags & MS_RDONLY) + mnt_flags |= MNT_READONLY; + if (flags & MS_NOSYMFOLLOW) + mnt_flags |= MNT_NOSYMFOLLOW; + + /* The default atime for remount is preservation */ + if ((flags & MS_REMOUNT) && + ((flags & (MS_NOATIME | MS_NODIRATIME | MS_RELATIME | + MS_STRICTATIME)) == 0)) { + mnt_flags &= ~MNT_ATIME_MASK; + mnt_flags |= path->mnt->mnt_flags & MNT_ATIME_MASK; + } + + sb_flags = flags & (SB_RDONLY | + SB_SYNCHRONOUS | + SB_MANDLOCK | + SB_DIRSYNC | + SB_SILENT | + SB_POSIXACL | + SB_LAZYTIME | + SB_I_VERSION); + + if ((flags & (MS_REMOUNT | MS_BIND)) == (MS_REMOUNT | MS_BIND)) + return do_reconfigure_mnt(path, mnt_flags); + if (flags & MS_REMOUNT) + return do_remount(path, flags, sb_flags, mnt_flags, data_page); + if (flags & MS_BIND) + return do_loopback(path, dev_name, flags & MS_REC); + if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + return do_change_type(path, flags); + if (flags & MS_MOVE) + return do_move_mount_old(path, dev_name); + + return do_new_mount(path, type_page, sb_flags, mnt_flags, dev_name, + data_page); +} + +long do_mount(const char *dev_name, const char __user *dir_name, + const char *type_page, unsigned long flags, void *data_page) +{ + struct path path; + int ret; + + ret = user_path_at(AT_FDCWD, dir_name, LOOKUP_FOLLOW, &path); + if (ret) + return ret; + ret = path_mount(dev_name, &path, type_page, flags, data_page); + path_put(&path); + return ret; +} + +static struct ucounts *inc_mnt_namespaces(struct user_namespace *ns) +{ + return inc_ucount(ns, current_euid(), UCOUNT_MNT_NAMESPACES); +} + +static void dec_mnt_namespaces(struct ucounts *ucounts) +{ + dec_ucount(ucounts, UCOUNT_MNT_NAMESPACES); +} + +static void free_mnt_ns(struct mnt_namespace *ns) +{ + if (!is_anon_ns(ns)) + ns_free_inum(&ns->ns); + dec_mnt_namespaces(ns->ucounts); + put_user_ns(ns->user_ns); + kfree(ns); +} + +/* + * Assign a sequence number so we can detect when we attempt to bind + * mount a reference to an older mount namespace into the current + * mount namespace, preventing reference counting loops. A 64bit + * number incrementing at 10Ghz will take 12,427 years to wrap which + * is effectively never, so we can ignore the possibility. + */ +static atomic64_t mnt_ns_seq = ATOMIC64_INIT(1); + +static struct mnt_namespace *alloc_mnt_ns(struct user_namespace *user_ns, bool anon) +{ + struct mnt_namespace *new_ns; + struct ucounts *ucounts; + int ret; + + ucounts = inc_mnt_namespaces(user_ns); + if (!ucounts) + return ERR_PTR(-ENOSPC); + + new_ns = kzalloc(sizeof(struct mnt_namespace), GFP_KERNEL_ACCOUNT); + if (!new_ns) { + dec_mnt_namespaces(ucounts); + return ERR_PTR(-ENOMEM); + } + if (!anon) { + ret = ns_alloc_inum(&new_ns->ns); + if (ret) { + kfree(new_ns); + dec_mnt_namespaces(ucounts); + return ERR_PTR(ret); + } + } + new_ns->ns.ops = &mntns_operations; + if (!anon) + new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); + refcount_set(&new_ns->ns.count, 1); + INIT_LIST_HEAD(&new_ns->list); + init_waitqueue_head(&new_ns->poll); + spin_lock_init(&new_ns->ns_lock); + new_ns->user_ns = get_user_ns(user_ns); + new_ns->ucounts = ucounts; + return new_ns; +} + +__latent_entropy +struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns, + struct user_namespace *user_ns, struct fs_struct *new_fs) +{ + struct mnt_namespace *new_ns; + struct vfsmount *rootmnt = NULL, *pwdmnt = NULL; + struct mount *p, *q; + struct mount *old; + struct mount *new; + int copy_flags; + + BUG_ON(!ns); + + if (likely(!(flags & CLONE_NEWNS))) { + get_mnt_ns(ns); + return ns; + } + + old = ns->root; + + new_ns = alloc_mnt_ns(user_ns, false); + if (IS_ERR(new_ns)) + return new_ns; + + namespace_lock(); + /* First pass: copy the tree topology */ + copy_flags = CL_COPY_UNBINDABLE | CL_EXPIRE; + if (user_ns != ns->user_ns) + copy_flags |= CL_SHARED_TO_SLAVE; + new = copy_tree(old, old->mnt.mnt_root, copy_flags); + if (IS_ERR(new)) { + namespace_unlock(); + free_mnt_ns(new_ns); + return ERR_CAST(new); + } + if (user_ns != ns->user_ns) { + lock_mount_hash(); + lock_mnt_tree(new); + unlock_mount_hash(); + } + new_ns->root = new; + list_add_tail(&new_ns->list, &new->mnt_list); + + /* + * Second pass: switch the tsk->fs->* elements and mark new vfsmounts + * as belonging to new namespace. We have already acquired a private + * fs_struct, so tsk->fs->lock is not needed. + */ + p = old; + q = new; + while (p) { + q->mnt_ns = new_ns; + new_ns->mounts++; + if (new_fs) { + if (&p->mnt == new_fs->root.mnt) { + new_fs->root.mnt = mntget(&q->mnt); + rootmnt = &p->mnt; + } + if (&p->mnt == new_fs->pwd.mnt) { + new_fs->pwd.mnt = mntget(&q->mnt); + pwdmnt = &p->mnt; + } + } + p = next_mnt(p, old); + q = next_mnt(q, new); + if (!q) + break; + // an mntns binding we'd skipped? + while (p->mnt.mnt_root != q->mnt.mnt_root) + p = next_mnt(skip_mnt_tree(p), old); + } + namespace_unlock(); + + if (rootmnt) + mntput(rootmnt); + if (pwdmnt) + mntput(pwdmnt); + + return new_ns; +} + +struct dentry *mount_subtree(struct vfsmount *m, const char *name) +{ + struct mount *mnt = real_mount(m); + struct mnt_namespace *ns; + struct super_block *s; + struct path path; + int err; + + ns = alloc_mnt_ns(&init_user_ns, true); + if (IS_ERR(ns)) { + mntput(m); + return ERR_CAST(ns); + } + mnt->mnt_ns = ns; + ns->root = mnt; + ns->mounts++; + list_add(&mnt->mnt_list, &ns->list); + + err = vfs_path_lookup(m->mnt_root, m, + name, LOOKUP_FOLLOW|LOOKUP_AUTOMOUNT, &path); + + put_mnt_ns(ns); + + if (err) + return ERR_PTR(err); + + /* trade a vfsmount reference for active sb one */ + s = path.mnt->mnt_sb; + atomic_inc(&s->s_active); + mntput(path.mnt); + /* lock the sucker */ + down_write(&s->s_umount); + /* ... and return the root of (sub)tree on it */ + return path.dentry; +} +EXPORT_SYMBOL(mount_subtree); + +SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, + char __user *, type, unsigned long, flags, void __user *, data) +{ + int ret; + char *kernel_type; + char *kernel_dev; + void *options; + + kernel_type = copy_mount_string(type); + ret = PTR_ERR(kernel_type); + if (IS_ERR(kernel_type)) + goto out_type; + + kernel_dev = copy_mount_string(dev_name); + ret = PTR_ERR(kernel_dev); + if (IS_ERR(kernel_dev)) + goto out_dev; + + options = copy_mount_options(data); + ret = PTR_ERR(options); + if (IS_ERR(options)) + goto out_data; + + ret = do_mount(kernel_dev, dir_name, kernel_type, flags, options); + + kfree(options); +out_data: + kfree(kernel_dev); +out_dev: + kfree(kernel_type); +out_type: + return ret; +} + +#define FSMOUNT_VALID_FLAGS \ + (MOUNT_ATTR_RDONLY | MOUNT_ATTR_NOSUID | MOUNT_ATTR_NODEV | \ + MOUNT_ATTR_NOEXEC | MOUNT_ATTR__ATIME | MOUNT_ATTR_NODIRATIME | \ + MOUNT_ATTR_NOSYMFOLLOW) + +#define MOUNT_SETATTR_VALID_FLAGS (FSMOUNT_VALID_FLAGS | MOUNT_ATTR_IDMAP) + +#define MOUNT_SETATTR_PROPAGATION_FLAGS \ + (MS_UNBINDABLE | MS_PRIVATE | MS_SLAVE | MS_SHARED) + +static unsigned int attr_flags_to_mnt_flags(u64 attr_flags) +{ + unsigned int mnt_flags = 0; + + if (attr_flags & MOUNT_ATTR_RDONLY) + mnt_flags |= MNT_READONLY; + if (attr_flags & MOUNT_ATTR_NOSUID) + mnt_flags |= MNT_NOSUID; + if (attr_flags & MOUNT_ATTR_NODEV) + mnt_flags |= MNT_NODEV; + if (attr_flags & MOUNT_ATTR_NOEXEC) + mnt_flags |= MNT_NOEXEC; + if (attr_flags & MOUNT_ATTR_NODIRATIME) + mnt_flags |= MNT_NODIRATIME; + if (attr_flags & MOUNT_ATTR_NOSYMFOLLOW) + mnt_flags |= MNT_NOSYMFOLLOW; + + return mnt_flags; +} + +/* + * Create a kernel mount representation for a new, prepared superblock + * (specified by fs_fd) and attach to an open_tree-like file descriptor. + */ +SYSCALL_DEFINE3(fsmount, int, fs_fd, unsigned int, flags, + unsigned int, attr_flags) +{ + struct mnt_namespace *ns; + struct fs_context *fc; + struct file *file; + struct path newmount; + struct mount *mnt; + struct fd f; + unsigned int mnt_flags = 0; + long ret; + + if (!may_mount()) + return -EPERM; + + if ((flags & ~(FSMOUNT_CLOEXEC)) != 0) + return -EINVAL; + + if (attr_flags & ~FSMOUNT_VALID_FLAGS) + return -EINVAL; + + mnt_flags = attr_flags_to_mnt_flags(attr_flags); + + switch (attr_flags & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_STRICTATIME: + break; + case MOUNT_ATTR_NOATIME: + mnt_flags |= MNT_NOATIME; + break; + case MOUNT_ATTR_RELATIME: + mnt_flags |= MNT_RELATIME; + break; + default: + return -EINVAL; + } + + f = fdget(fs_fd); + if (!f.file) + return -EBADF; + + ret = -EINVAL; + if (f.file->f_op != &fscontext_fops) + goto err_fsfd; + + fc = f.file->private_data; + + ret = mutex_lock_interruptible(&fc->uapi_mutex); + if (ret < 0) + goto err_fsfd; + + /* There must be a valid superblock or we can't mount it */ + ret = -EINVAL; + if (!fc->root) + goto err_unlock; + + ret = -EPERM; + if (mount_too_revealing(fc->root->d_sb, &mnt_flags)) { + pr_warn("VFS: Mount too revealing\n"); + goto err_unlock; + } + + ret = -EBUSY; + if (fc->phase != FS_CONTEXT_AWAITING_MOUNT) + goto err_unlock; + + if (fc->sb_flags & SB_MANDLOCK) + warn_mandlock(); + + newmount.mnt = vfs_create_mount(fc); + if (IS_ERR(newmount.mnt)) { + ret = PTR_ERR(newmount.mnt); + goto err_unlock; + } + newmount.dentry = dget(fc->root); + newmount.mnt->mnt_flags = mnt_flags; + + /* We've done the mount bit - now move the file context into more or + * less the same state as if we'd done an fspick(). We don't want to + * do any memory allocation or anything like that at this point as we + * don't want to have to handle any errors incurred. + */ + vfs_clean_context(fc); + + ns = alloc_mnt_ns(current->nsproxy->mnt_ns->user_ns, true); + if (IS_ERR(ns)) { + ret = PTR_ERR(ns); + goto err_path; + } + mnt = real_mount(newmount.mnt); + mnt->mnt_ns = ns; + ns->root = mnt; + ns->mounts = 1; + list_add(&mnt->mnt_list, &ns->list); + mntget(newmount.mnt); + + /* Attach to an apparent O_PATH fd with a note that we need to unmount + * it, not just simply put it. + */ + file = dentry_open(&newmount, O_PATH, fc->cred); + if (IS_ERR(file)) { + dissolve_on_fput(newmount.mnt); + ret = PTR_ERR(file); + goto err_path; + } + file->f_mode |= FMODE_NEED_UNMOUNT; + + ret = get_unused_fd_flags((flags & FSMOUNT_CLOEXEC) ? O_CLOEXEC : 0); + if (ret >= 0) + fd_install(ret, file); + else + fput(file); + +err_path: + path_put(&newmount); +err_unlock: + mutex_unlock(&fc->uapi_mutex); +err_fsfd: + fdput(f); + return ret; +} + +/* + * Move a mount from one place to another. In combination with + * fsopen()/fsmount() this is used to install a new mount and in combination + * with open_tree(OPEN_TREE_CLONE [| AT_RECURSIVE]) it can be used to copy + * a mount subtree. + * + * Note the flags value is a combination of MOVE_MOUNT_* flags. + */ +SYSCALL_DEFINE5(move_mount, + int, from_dfd, const char __user *, from_pathname, + int, to_dfd, const char __user *, to_pathname, + unsigned int, flags) +{ + struct path from_path, to_path; + unsigned int lflags; + int ret = 0; + + if (!may_mount()) + return -EPERM; + + if (flags & ~MOVE_MOUNT__MASK) + return -EINVAL; + + if ((flags & (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) == + (MOVE_MOUNT_BENEATH | MOVE_MOUNT_SET_GROUP)) + return -EINVAL; + + /* If someone gives a pathname, they aren't permitted to move + * from an fd that requires unmount as we can't get at the flag + * to clear it afterwards. + */ + lflags = 0; + if (flags & MOVE_MOUNT_F_SYMLINKS) lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_F_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; + if (flags & MOVE_MOUNT_F_EMPTY_PATH) lflags |= LOOKUP_EMPTY; + + ret = user_path_at(from_dfd, from_pathname, lflags, &from_path); + if (ret < 0) + return ret; + + lflags = 0; + if (flags & MOVE_MOUNT_T_SYMLINKS) lflags |= LOOKUP_FOLLOW; + if (flags & MOVE_MOUNT_T_AUTOMOUNTS) lflags |= LOOKUP_AUTOMOUNT; + if (flags & MOVE_MOUNT_T_EMPTY_PATH) lflags |= LOOKUP_EMPTY; + + ret = user_path_at(to_dfd, to_pathname, lflags, &to_path); + if (ret < 0) + goto out_from; + + ret = security_move_mount(&from_path, &to_path); + if (ret < 0) + goto out_to; + + if (flags & MOVE_MOUNT_SET_GROUP) + ret = do_set_group(&from_path, &to_path); + else + ret = do_move_mount(&from_path, &to_path, + (flags & MOVE_MOUNT_BENEATH)); + +out_to: + path_put(&to_path); +out_from: + path_put(&from_path); + return ret; +} + +/* + * Return true if path is reachable from root + * + * namespace_sem or mount_lock is held + */ +bool is_path_reachable(struct mount *mnt, struct dentry *dentry, + const struct path *root) +{ + while (&mnt->mnt != root->mnt && mnt_has_parent(mnt)) { + dentry = mnt->mnt_mountpoint; + mnt = mnt->mnt_parent; + } + return &mnt->mnt == root->mnt && is_subdir(dentry, root->dentry); +} + +bool path_is_under(const struct path *path1, const struct path *path2) +{ + bool res; + read_seqlock_excl(&mount_lock); + res = is_path_reachable(real_mount(path1->mnt), path1->dentry, path2); + read_sequnlock_excl(&mount_lock); + return res; +} +EXPORT_SYMBOL(path_is_under); + +/* + * pivot_root Semantics: + * Moves the root file system of the current process to the directory put_old, + * makes new_root as the new root file system of the current process, and sets + * root/cwd of all processes which had them on the current root to new_root. + * + * Restrictions: + * The new_root and put_old must be directories, and must not be on the + * same file system as the current process root. The put_old must be + * underneath new_root, i.e. adding a non-zero number of /.. to the string + * pointed to by put_old must yield the same directory as new_root. No other + * file system may be mounted on put_old. After all, new_root is a mountpoint. + * + * Also, the current root cannot be on the 'rootfs' (initial ramfs) filesystem. + * See Documentation/filesystems/ramfs-rootfs-initramfs.rst for alternatives + * in this situation. + * + * Notes: + * - we don't move root/cwd if they are not at the root (reason: if something + * cared enough to change them, it's probably wrong to force them elsewhere) + * - it's okay to pick a root that isn't the root of a file system, e.g. + * /nfs/my_root where /nfs is the mount point. It must be a mountpoint, + * though, so you may need to say mount --bind /nfs/my_root /nfs/my_root + * first. + */ +SYSCALL_DEFINE2(pivot_root, const char __user *, new_root, + const char __user *, put_old) +{ + struct path new, old, root; + struct mount *new_mnt, *root_mnt, *old_mnt, *root_parent, *ex_parent; + struct mountpoint *old_mp, *root_mp; + int error; + + if (!may_mount()) + return -EPERM; + + error = user_path_at(AT_FDCWD, new_root, + LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &new); + if (error) + goto out0; + + error = user_path_at(AT_FDCWD, put_old, + LOOKUP_FOLLOW | LOOKUP_DIRECTORY, &old); + if (error) + goto out1; + + error = security_sb_pivotroot(&old, &new); + if (error) + goto out2; + + get_fs_root(current->fs, &root); + old_mp = lock_mount(&old); + error = PTR_ERR(old_mp); + if (IS_ERR(old_mp)) + goto out3; + + error = -EINVAL; + new_mnt = real_mount(new.mnt); + root_mnt = real_mount(root.mnt); + old_mnt = real_mount(old.mnt); + ex_parent = new_mnt->mnt_parent; + root_parent = root_mnt->mnt_parent; + if (IS_MNT_SHARED(old_mnt) || + IS_MNT_SHARED(ex_parent) || + IS_MNT_SHARED(root_parent)) + goto out4; + if (!check_mnt(root_mnt) || !check_mnt(new_mnt)) + goto out4; + if (new_mnt->mnt.mnt_flags & MNT_LOCKED) + goto out4; + error = -ENOENT; + if (d_unlinked(new.dentry)) + goto out4; + error = -EBUSY; + if (new_mnt == root_mnt || old_mnt == root_mnt) + goto out4; /* loop, on the same file system */ + error = -EINVAL; + if (!path_mounted(&root)) + goto out4; /* not a mountpoint */ + if (!mnt_has_parent(root_mnt)) + goto out4; /* not attached */ + if (!path_mounted(&new)) + goto out4; /* not a mountpoint */ + if (!mnt_has_parent(new_mnt)) + goto out4; /* not attached */ + /* make sure we can reach put_old from new_root */ + if (!is_path_reachable(old_mnt, old.dentry, &new)) + goto out4; + /* make certain new is below the root */ + if (!is_path_reachable(new_mnt, new.dentry, &root)) + goto out4; + lock_mount_hash(); + umount_mnt(new_mnt); + root_mp = unhash_mnt(root_mnt); /* we'll need its mountpoint */ + if (root_mnt->mnt.mnt_flags & MNT_LOCKED) { + new_mnt->mnt.mnt_flags |= MNT_LOCKED; + root_mnt->mnt.mnt_flags &= ~MNT_LOCKED; + } + /* mount old root on put_old */ + attach_mnt(root_mnt, old_mnt, old_mp, false); + /* mount new_root on / */ + attach_mnt(new_mnt, root_parent, root_mp, false); + mnt_add_count(root_parent, -1); + touch_mnt_namespace(current->nsproxy->mnt_ns); + /* A moved mount should not expire automatically */ + list_del_init(&new_mnt->mnt_expire); + put_mountpoint(root_mp); + unlock_mount_hash(); + chroot_fs_refs(&root, &new); + error = 0; +out4: + unlock_mount(old_mp); + if (!error) + mntput_no_expire(ex_parent); +out3: + path_put(&root); +out2: + path_put(&old); +out1: + path_put(&new); +out0: + return error; +} + +static unsigned int recalc_flags(struct mount_kattr *kattr, struct mount *mnt) +{ + unsigned int flags = mnt->mnt.mnt_flags; + + /* flags to clear */ + flags &= ~kattr->attr_clr; + /* flags to raise */ + flags |= kattr->attr_set; + + return flags; +} + +static int can_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) +{ + struct vfsmount *m = &mnt->mnt; + struct user_namespace *fs_userns = m->mnt_sb->s_user_ns; + + if (!kattr->mnt_idmap) + return 0; + + /* + * Creating an idmapped mount with the filesystem wide idmapping + * doesn't make sense so block that. We don't allow mushy semantics. + */ + if (!check_fsmapping(kattr->mnt_idmap, m->mnt_sb)) + return -EINVAL; + + /* + * Once a mount has been idmapped we don't allow it to change its + * mapping. It makes things simpler and callers can just create + * another bind-mount they can idmap if they want to. + */ + if (is_idmapped_mnt(m)) + return -EPERM; + + /* The underlying filesystem doesn't support idmapped mounts yet. */ + if (!(m->mnt_sb->s_type->fs_flags & FS_ALLOW_IDMAP)) + return -EINVAL; + + /* We're not controlling the superblock. */ + if (!ns_capable(fs_userns, CAP_SYS_ADMIN)) + return -EPERM; + + /* Mount has already been visible in the filesystem hierarchy. */ + if (!is_anon_ns(mnt->mnt_ns)) + return -EINVAL; + + return 0; +} + +/** + * mnt_allow_writers() - check whether the attribute change allows writers + * @kattr: the new mount attributes + * @mnt: the mount to which @kattr will be applied + * + * Check whether thew new mount attributes in @kattr allow concurrent writers. + * + * Return: true if writers need to be held, false if not + */ +static inline bool mnt_allow_writers(const struct mount_kattr *kattr, + const struct mount *mnt) +{ + return (!(kattr->attr_set & MNT_READONLY) || + (mnt->mnt.mnt_flags & MNT_READONLY)) && + !kattr->mnt_idmap; +} + +static int mount_setattr_prepare(struct mount_kattr *kattr, struct mount *mnt) +{ + struct mount *m; + int err; + + for (m = mnt; m; m = next_mnt(m, mnt)) { + if (!can_change_locked_flags(m, recalc_flags(kattr, m))) { + err = -EPERM; + break; + } + + err = can_idmap_mount(kattr, m); + if (err) + break; + + if (!mnt_allow_writers(kattr, m)) { + err = mnt_hold_writers(m); + if (err) + break; + } + + if (!kattr->recurse) + return 0; + } + + if (err) { + struct mount *p; + + /* + * If we had to call mnt_hold_writers() MNT_WRITE_HOLD will + * be set in @mnt_flags. The loop unsets MNT_WRITE_HOLD for all + * mounts and needs to take care to include the first mount. + */ + for (p = mnt; p; p = next_mnt(p, mnt)) { + /* If we had to hold writers unblock them. */ + if (p->mnt.mnt_flags & MNT_WRITE_HOLD) + mnt_unhold_writers(p); + + /* + * We're done once the first mount we changed got + * MNT_WRITE_HOLD unset. + */ + if (p == m) + break; + } + } + return err; +} + +static void do_idmap_mount(const struct mount_kattr *kattr, struct mount *mnt) +{ + if (!kattr->mnt_idmap) + return; + + /* + * Pairs with smp_load_acquire() in mnt_idmap(). + * + * Since we only allow a mount to change the idmapping once and + * verified this in can_idmap_mount() we know that the mount has + * @nop_mnt_idmap attached to it. So there's no need to drop any + * references. + */ + smp_store_release(&mnt->mnt.mnt_idmap, mnt_idmap_get(kattr->mnt_idmap)); +} + +static void mount_setattr_commit(struct mount_kattr *kattr, struct mount *mnt) +{ + struct mount *m; + + for (m = mnt; m; m = next_mnt(m, mnt)) { + unsigned int flags; + + do_idmap_mount(kattr, m); + flags = recalc_flags(kattr, m); + WRITE_ONCE(m->mnt.mnt_flags, flags); + + /* If we had to hold writers unblock them. */ + if (m->mnt.mnt_flags & MNT_WRITE_HOLD) + mnt_unhold_writers(m); + + if (kattr->propagation) + change_mnt_propagation(m, kattr->propagation); + if (!kattr->recurse) + break; + } + touch_mnt_namespace(mnt->mnt_ns); +} + +static int do_mount_setattr(struct path *path, struct mount_kattr *kattr) +{ + struct mount *mnt = real_mount(path->mnt); + int err = 0; + + if (!path_mounted(path)) + return -EINVAL; + + if (kattr->mnt_userns) { + struct mnt_idmap *mnt_idmap; + + mnt_idmap = alloc_mnt_idmap(kattr->mnt_userns); + if (IS_ERR(mnt_idmap)) + return PTR_ERR(mnt_idmap); + kattr->mnt_idmap = mnt_idmap; + } + + if (kattr->propagation) { + /* + * Only take namespace_lock() if we're actually changing + * propagation. + */ + namespace_lock(); + if (kattr->propagation == MS_SHARED) { + err = invent_group_ids(mnt, kattr->recurse); + if (err) { + namespace_unlock(); + return err; + } + } + } + + err = -EINVAL; + lock_mount_hash(); + + /* Ensure that this isn't anything purely vfs internal. */ + if (!is_mounted(&mnt->mnt)) + goto out; + + /* + * If this is an attached mount make sure it's located in the callers + * mount namespace. If it's not don't let the caller interact with it. + * If this is a detached mount make sure it has an anonymous mount + * namespace attached to it, i.e. we've created it via OPEN_TREE_CLONE. + */ + if (!(mnt_has_parent(mnt) ? check_mnt(mnt) : is_anon_ns(mnt->mnt_ns))) + goto out; + + /* + * First, we get the mount tree in a shape where we can change mount + * properties without failure. If we succeeded to do so we commit all + * changes and if we failed we clean up. + */ + err = mount_setattr_prepare(kattr, mnt); + if (!err) + mount_setattr_commit(kattr, mnt); + +out: + unlock_mount_hash(); + + if (kattr->propagation) { + if (err) + cleanup_group_ids(mnt, NULL); + namespace_unlock(); + } + + return err; +} + +static int build_mount_idmapped(const struct mount_attr *attr, size_t usize, + struct mount_kattr *kattr, unsigned int flags) +{ + int err = 0; + struct ns_common *ns; + struct user_namespace *mnt_userns; + struct fd f; + + if (!((attr->attr_set | attr->attr_clr) & MOUNT_ATTR_IDMAP)) + return 0; + + /* + * We currently do not support clearing an idmapped mount. If this ever + * is a use-case we can revisit this but for now let's keep it simple + * and not allow it. + */ + if (attr->attr_clr & MOUNT_ATTR_IDMAP) + return -EINVAL; + + if (attr->userns_fd > INT_MAX) + return -EINVAL; + + f = fdget(attr->userns_fd); + if (!f.file) + return -EBADF; + + if (!proc_ns_file(f.file)) { + err = -EINVAL; + goto out_fput; + } + + ns = get_proc_ns(file_inode(f.file)); + if (ns->ops->type != CLONE_NEWUSER) { + err = -EINVAL; + goto out_fput; + } + + /* + * The initial idmapping cannot be used to create an idmapped + * mount. We use the initial idmapping as an indicator of a mount + * that is not idmapped. It can simply be passed into helpers that + * are aware of idmapped mounts as a convenient shortcut. A user + * can just create a dedicated identity mapping to achieve the same + * result. + */ + mnt_userns = container_of(ns, struct user_namespace, ns); + if (mnt_userns == &init_user_ns) { + err = -EPERM; + goto out_fput; + } + + /* We're not controlling the target namespace. */ + if (!ns_capable(mnt_userns, CAP_SYS_ADMIN)) { + err = -EPERM; + goto out_fput; + } + + kattr->mnt_userns = get_user_ns(mnt_userns); + +out_fput: + fdput(f); + return err; +} + +static int build_mount_kattr(const struct mount_attr *attr, size_t usize, + struct mount_kattr *kattr, unsigned int flags) +{ + unsigned int lookup_flags = LOOKUP_AUTOMOUNT | LOOKUP_FOLLOW; + + if (flags & AT_NO_AUTOMOUNT) + lookup_flags &= ~LOOKUP_AUTOMOUNT; + if (flags & AT_SYMLINK_NOFOLLOW) + lookup_flags &= ~LOOKUP_FOLLOW; + if (flags & AT_EMPTY_PATH) + lookup_flags |= LOOKUP_EMPTY; + + *kattr = (struct mount_kattr) { + .lookup_flags = lookup_flags, + .recurse = !!(flags & AT_RECURSIVE), + }; + + if (attr->propagation & ~MOUNT_SETATTR_PROPAGATION_FLAGS) + return -EINVAL; + if (hweight32(attr->propagation & MOUNT_SETATTR_PROPAGATION_FLAGS) > 1) + return -EINVAL; + kattr->propagation = attr->propagation; + + if ((attr->attr_set | attr->attr_clr) & ~MOUNT_SETATTR_VALID_FLAGS) + return -EINVAL; + + kattr->attr_set = attr_flags_to_mnt_flags(attr->attr_set); + kattr->attr_clr = attr_flags_to_mnt_flags(attr->attr_clr); + + /* + * Since the MOUNT_ATTR_<atime> values are an enum, not a bitmap, + * users wanting to transition to a different atime setting cannot + * simply specify the atime setting in @attr_set, but must also + * specify MOUNT_ATTR__ATIME in the @attr_clr field. + * So ensure that MOUNT_ATTR__ATIME can't be partially set in + * @attr_clr and that @attr_set can't have any atime bits set if + * MOUNT_ATTR__ATIME isn't set in @attr_clr. + */ + if (attr->attr_clr & MOUNT_ATTR__ATIME) { + if ((attr->attr_clr & MOUNT_ATTR__ATIME) != MOUNT_ATTR__ATIME) + return -EINVAL; + + /* + * Clear all previous time settings as they are mutually + * exclusive. + */ + kattr->attr_clr |= MNT_RELATIME | MNT_NOATIME; + switch (attr->attr_set & MOUNT_ATTR__ATIME) { + case MOUNT_ATTR_RELATIME: + kattr->attr_set |= MNT_RELATIME; + break; + case MOUNT_ATTR_NOATIME: + kattr->attr_set |= MNT_NOATIME; + break; + case MOUNT_ATTR_STRICTATIME: + break; + default: + return -EINVAL; + } + } else { + if (attr->attr_set & MOUNT_ATTR__ATIME) + return -EINVAL; + } + + return build_mount_idmapped(attr, usize, kattr, flags); +} + +static void finish_mount_kattr(struct mount_kattr *kattr) +{ + put_user_ns(kattr->mnt_userns); + kattr->mnt_userns = NULL; + + if (kattr->mnt_idmap) + mnt_idmap_put(kattr->mnt_idmap); +} + +SYSCALL_DEFINE5(mount_setattr, int, dfd, const char __user *, path, + unsigned int, flags, struct mount_attr __user *, uattr, + size_t, usize) +{ + int err; + struct path target; + struct mount_attr attr; + struct mount_kattr kattr; + + BUILD_BUG_ON(sizeof(struct mount_attr) != MOUNT_ATTR_SIZE_VER0); + + if (flags & ~(AT_EMPTY_PATH | + AT_RECURSIVE | + AT_SYMLINK_NOFOLLOW | + AT_NO_AUTOMOUNT)) + return -EINVAL; + + if (unlikely(usize > PAGE_SIZE)) + return -E2BIG; + if (unlikely(usize < MOUNT_ATTR_SIZE_VER0)) + return -EINVAL; + + if (!may_mount()) + return -EPERM; + + err = copy_struct_from_user(&attr, sizeof(attr), uattr, usize); + if (err) + return err; + + /* Don't bother walking through the mounts if this is a nop. */ + if (attr.attr_set == 0 && + attr.attr_clr == 0 && + attr.propagation == 0) + return 0; + + err = build_mount_kattr(&attr, usize, &kattr, flags); + if (err) + return err; + + err = user_path_at(dfd, path, kattr.lookup_flags, &target); + if (!err) { + err = do_mount_setattr(&target, &kattr); + path_put(&target); + } + finish_mount_kattr(&kattr); + return err; +} + +static void __init init_mount_tree(void) +{ + struct vfsmount *mnt; + struct mount *m; + struct mnt_namespace *ns; + struct path root; + + mnt = vfs_kern_mount(&rootfs_fs_type, 0, "rootfs", NULL); + if (IS_ERR(mnt)) + panic("Can't create rootfs"); + + ns = alloc_mnt_ns(&init_user_ns, false); + if (IS_ERR(ns)) + panic("Can't allocate initial namespace"); + m = real_mount(mnt); + m->mnt_ns = ns; + ns->root = m; + ns->mounts = 1; + list_add(&m->mnt_list, &ns->list); + init_task.nsproxy->mnt_ns = ns; + get_mnt_ns(ns); + + root.mnt = mnt; + root.dentry = mnt->mnt_root; + mnt->mnt_flags |= MNT_LOCKED; + + set_fs_pwd(current->fs, &root); + set_fs_root(current->fs, &root); +} + +void __init mnt_init(void) +{ + int err; + + mnt_cache = kmem_cache_create("mnt_cache", sizeof(struct mount), + 0, SLAB_HWCACHE_ALIGN|SLAB_PANIC|SLAB_ACCOUNT, NULL); + + mount_hashtable = alloc_large_system_hash("Mount-cache", + sizeof(struct hlist_head), + mhash_entries, 19, + HASH_ZERO, + &m_hash_shift, &m_hash_mask, 0, 0); + mountpoint_hashtable = alloc_large_system_hash("Mountpoint-cache", + sizeof(struct hlist_head), + mphash_entries, 19, + HASH_ZERO, + &mp_hash_shift, &mp_hash_mask, 0, 0); + + if (!mount_hashtable || !mountpoint_hashtable) + panic("Failed to allocate mount hash table\n"); + + kernfs_init(); + + err = sysfs_init(); + if (err) + printk(KERN_WARNING "%s: sysfs_init error: %d\n", + __func__, err); + fs_kobj = kobject_create_and_add("fs", NULL); + if (!fs_kobj) + printk(KERN_WARNING "%s: kobj create error\n", __func__); + shmem_init(); + init_rootfs(); + init_mount_tree(); +} + +void put_mnt_ns(struct mnt_namespace *ns) +{ + if (!refcount_dec_and_test(&ns->ns.count)) + return; + drop_collected_mounts(&ns->root->mnt); + free_mnt_ns(ns); +} + +struct vfsmount *kern_mount(struct file_system_type *type) +{ + struct vfsmount *mnt; + mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, NULL); + if (!IS_ERR(mnt)) { + /* + * it is a longterm mount, don't release mnt until + * we unmount before file sys is unregistered + */ + real_mount(mnt)->mnt_ns = MNT_NS_INTERNAL; + } + return mnt; +} +EXPORT_SYMBOL_GPL(kern_mount); + +void kern_unmount(struct vfsmount *mnt) +{ + /* release long term mount so mount point can be released */ + if (!IS_ERR(mnt)) { + mnt_make_shortterm(mnt); + synchronize_rcu(); /* yecchhh... */ + mntput(mnt); + } +} +EXPORT_SYMBOL(kern_unmount); + +void kern_unmount_array(struct vfsmount *mnt[], unsigned int num) +{ + unsigned int i; + + for (i = 0; i < num; i++) + mnt_make_shortterm(mnt[i]); + synchronize_rcu_expedited(); + for (i = 0; i < num; i++) + mntput(mnt[i]); +} +EXPORT_SYMBOL(kern_unmount_array); + +bool our_mnt(struct vfsmount *mnt) +{ + return check_mnt(real_mount(mnt)); +} + +bool current_chrooted(void) +{ + /* Does the current process have a non-standard root */ + struct path ns_root; + struct path fs_root; + bool chrooted; + + /* Find the namespace root */ + ns_root.mnt = ¤t->nsproxy->mnt_ns->root->mnt; + ns_root.dentry = ns_root.mnt->mnt_root; + path_get(&ns_root); + while (d_mountpoint(ns_root.dentry) && follow_down_one(&ns_root)) + ; + + get_fs_root(current->fs, &fs_root); + + chrooted = !path_equal(&fs_root, &ns_root); + + path_put(&fs_root); + path_put(&ns_root); + + return chrooted; +} + +static bool mnt_already_visible(struct mnt_namespace *ns, + const struct super_block *sb, + int *new_mnt_flags) +{ + int new_flags = *new_mnt_flags; + struct mount *mnt; + bool visible = false; + + down_read(&namespace_sem); + lock_ns_list(ns); + list_for_each_entry(mnt, &ns->list, mnt_list) { + struct mount *child; + int mnt_flags; + + if (mnt_is_cursor(mnt)) + continue; + + if (mnt->mnt.mnt_sb->s_type != sb->s_type) + continue; + + /* This mount is not fully visible if it's root directory + * is not the root directory of the filesystem. + */ + if (mnt->mnt.mnt_root != mnt->mnt.mnt_sb->s_root) + continue; + + /* A local view of the mount flags */ + mnt_flags = mnt->mnt.mnt_flags; + + /* Don't miss readonly hidden in the superblock flags */ + if (sb_rdonly(mnt->mnt.mnt_sb)) + mnt_flags |= MNT_LOCK_READONLY; + + /* Verify the mount flags are equal to or more permissive + * than the proposed new mount. + */ + if ((mnt_flags & MNT_LOCK_READONLY) && + !(new_flags & MNT_READONLY)) + continue; + if ((mnt_flags & MNT_LOCK_ATIME) && + ((mnt_flags & MNT_ATIME_MASK) != (new_flags & MNT_ATIME_MASK))) + continue; + + /* This mount is not fully visible if there are any + * locked child mounts that cover anything except for + * empty directories. + */ + list_for_each_entry(child, &mnt->mnt_mounts, mnt_child) { + struct inode *inode = child->mnt_mountpoint->d_inode; + /* Only worry about locked mounts */ + if (!(child->mnt.mnt_flags & MNT_LOCKED)) + continue; + /* Is the directory permanetly empty? */ + if (!is_empty_dir_inode(inode)) + goto next; + } + /* Preserve the locked attributes */ + *new_mnt_flags |= mnt_flags & (MNT_LOCK_READONLY | \ + MNT_LOCK_ATIME); + visible = true; + goto found; + next: ; + } +found: + unlock_ns_list(ns); + up_read(&namespace_sem); + return visible; +} + +static bool mount_too_revealing(const struct super_block *sb, int *new_mnt_flags) +{ + const unsigned long required_iflags = SB_I_NOEXEC | SB_I_NODEV; + struct mnt_namespace *ns = current->nsproxy->mnt_ns; + unsigned long s_iflags; + + if (ns->user_ns == &init_user_ns) + return false; + + /* Can this filesystem be too revealing? */ + s_iflags = sb->s_iflags; + if (!(s_iflags & SB_I_USERNS_VISIBLE)) + return false; + + if ((s_iflags & required_iflags) != required_iflags) { + WARN_ONCE(1, "Expected s_iflags to contain 0x%lx\n", + required_iflags); + return true; + } + + return !mnt_already_visible(ns, sb, new_mnt_flags); +} + +bool mnt_may_suid(struct vfsmount *mnt) +{ + /* + * Foreign mounts (accessed via fchdir or through /proc + * symlinks) are always treated as if they are nosuid. This + * prevents namespaces from trusting potentially unsafe + * suid/sgid bits, file caps, or security labels that originate + * in other namespaces. + */ + return !(mnt->mnt_flags & MNT_NOSUID) && check_mnt(real_mount(mnt)) && + current_in_userns(mnt->mnt_sb->s_user_ns); +} + +static struct ns_common *mntns_get(struct task_struct *task) +{ + struct ns_common *ns = NULL; + struct nsproxy *nsproxy; + + task_lock(task); + nsproxy = task->nsproxy; + if (nsproxy) { + ns = &nsproxy->mnt_ns->ns; + get_mnt_ns(to_mnt_ns(ns)); + } + task_unlock(task); + + return ns; +} + +static void mntns_put(struct ns_common *ns) +{ + put_mnt_ns(to_mnt_ns(ns)); +} + +static int mntns_install(struct nsset *nsset, struct ns_common *ns) +{ + struct nsproxy *nsproxy = nsset->nsproxy; + struct fs_struct *fs = nsset->fs; + struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; + struct user_namespace *user_ns = nsset->cred->user_ns; + struct path root; + int err; + + if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable(user_ns, CAP_SYS_CHROOT) || + !ns_capable(user_ns, CAP_SYS_ADMIN)) + return -EPERM; + + if (is_anon_ns(mnt_ns)) + return -EINVAL; + + if (fs->users != 1) + return -EINVAL; + + get_mnt_ns(mnt_ns); + old_mnt_ns = nsproxy->mnt_ns; + nsproxy->mnt_ns = mnt_ns; + + /* Find the root */ + err = vfs_path_lookup(mnt_ns->root->mnt.mnt_root, &mnt_ns->root->mnt, + "/", LOOKUP_DOWN, &root); + if (err) { + /* revert to old namespace */ + nsproxy->mnt_ns = old_mnt_ns; + put_mnt_ns(mnt_ns); + return err; + } + + put_mnt_ns(old_mnt_ns); + + /* Update the pwd and root */ + set_fs_pwd(fs, &root); + set_fs_root(fs, &root); + + path_put(&root); + return 0; +} + +static struct user_namespace *mntns_owner(struct ns_common *ns) +{ + return to_mnt_ns(ns)->user_ns; +} + +const struct proc_ns_operations mntns_operations = { + .name = "mnt", + .type = CLONE_NEWNS, + .get = mntns_get, + .put = mntns_put, + .install = mntns_install, + .owner = mntns_owner, +}; + +#ifdef CONFIG_SYSCTL +static struct ctl_table fs_namespace_sysctls[] = { + { + .procname = "mount-max", + .data = &sysctl_mount_max, + .maxlen = sizeof(unsigned int), + .mode = 0644, + .proc_handler = proc_dointvec_minmax, + .extra1 = SYSCTL_ONE, + }, + { } +}; + +static int __init init_fs_namespace_sysctls(void) +{ + register_sysctl_init("fs", fs_namespace_sysctls); + return 0; +} +fs_initcall(init_fs_namespace_sysctls); + +#endif /* CONFIG_SYSCTL */ |