diff options
Diffstat (limited to 'fs/namespace.c')
| -rw-r--r-- | fs/namespace.c | 3504 |
1 files changed, 3504 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c new file mode 100644 index 000000000..396ff1bcf --- /dev/null +++ b/fs/namespace.c @@ -0,0 +1,3504 @@ +/* + * linux/fs/namespace.c + * + * (C) Copyright Al Viro 2000, 2001 + * Released under GPL v2. + * + * 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/uaccess.h> +#include <linux/proc_ns.h> +#include <linux/magic.h> +#include <linux/bootmem.h> +#include <linux/task_work.h> +#include <linux/sched/task.h> + +#include "pnode.h" +#include "internal.h" + +/* Maximum number of mounts in a mount namespace */ +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); + +/* /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 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 + */ +unsigned int mnt_get_count(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_count; + } + + return count; +#else + return mnt->mnt_count; +#endif +} + +static void drop_mountpoint(struct fs_pin *p) +{ + struct mount *m = container_of(p, struct mount, mnt_umount); + dput(m->mnt_ex_mountpoint); + pin_remove(p); + mntput(&m->mnt); +} + +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); + 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_fs_pin(&mnt->mnt_umount, drop_mountpoint); + } + 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. + */ +int __mnt_is_readonly(struct vfsmount *mnt) +{ + if (mnt->mnt_flags & MNT_READONLY) + return 1; + if (sb_rdonly(mnt->mnt_sb)) + return 1; + return 0; +} +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 (mnt->mnt_sb->s_readonly_remount) + return 1; + /* Order wrt setting s_flags/s_readonly_remount in do_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(); + while (READ_ONCE(mnt->mnt.mnt_flags) & MNT_WRITE_HOLD) + cpu_relax(); + /* + * After the slowpath clears MNT_WRITE_HOLD, mnt_is_readonly will + * be set to match its requirements. So we must not load that until + * MNT_WRITE_HOLD is cleared. + */ + 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_clone_write - get write access to a mount + * @mnt: the mount on which to take a write + * + * This is effectively like mnt_want_write, except + * it must only be used to take an extra write reference + * on a mountpoint that we already know has a write reference + * on it. This allows some optimisation. + * + * After finished, mnt_drop_write must be called as usual to + * drop the reference. + */ +int mnt_clone_write(struct vfsmount *mnt) +{ + /* superblock may be r/o */ + if (__mnt_is_readonly(mnt)) + return -EROFS; + preempt_disable(); + mnt_inc_writers(real_mount(mnt)); + preempt_enable(); + return 0; +} +EXPORT_SYMBOL_GPL(mnt_clone_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 it takes a file and can + * do some optimisations if the file is open for write already + */ +int __mnt_want_write_file(struct file *file) +{ + if (!(file->f_mode & FMODE_WRITER)) + return __mnt_want_write(file->f_path.mnt); + else + return mnt_clone_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 it takes a file and can + * do some optimisations if the file is open for write already + */ +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) +{ + __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); + +static int mnt_make_readonly(struct mount *mnt) +{ + int ret = 0; + + lock_mount_hash(); + 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) + ret = -EBUSY; + else + mnt->mnt.mnt_flags |= MNT_READONLY; + /* + * 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; + unlock_mount_hash(); + return ret; +} + +static void __mnt_unmake_readonly(struct mount *mnt) +{ + lock_mount_hash(); + mnt->mnt.mnt_flags &= ~MNT_READONLY; + unlock_mount_hash(); +} + +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)) { + mnt->mnt.mnt_flags |= MNT_WRITE_HOLD; + smp_mb(); + if (mnt_get_writers(mnt) > 0) { + err = -EBUSY; + break; + } + } + } + if (!err && atomic_long_read(&sb->s_remove_count)) + err = -EBUSY; + + if (!err) { + sb->s_readonly_remount = 1; + smp_wmb(); + } + 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) +{ + 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 */ +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; +} + +/* + * find the first mount at @dentry on vfsmount @mnt. + * call under rcu_read_lock() + */ +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; +} + +/* + * __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; + + if (!d_mountpoint(dentry)) + goto out; + + down_read(&namespace_sem); + list_for_each_entry(mnt, &ns->list, mnt_list) { + is_covered = (mnt->mnt_mountpoint == dentry); + if (is_covered) + break; + } + up_read(&namespace_sem); +out: + 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 = 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; +} + +static void put_mountpoint(struct mountpoint *mp) +{ + 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); + hlist_del(&mp->m_hash); + kfree(mp); + } +} + +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 void unhash_mnt(struct mount *mnt) +{ + 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); + put_mountpoint(mnt->mnt_mp); + mnt->mnt_mp = NULL; +} + +/* + * vfsmount lock must be held for write + */ +static void detach_mnt(struct mount *mnt, struct path *old_path) +{ + old_path->dentry = mnt->mnt_mountpoint; + old_path->mnt = &mnt->mnt_parent->mnt; + unhash_mnt(mnt); +} + +/* + * vfsmount lock must be held for write + */ +static void umount_mnt(struct mount *mnt) +{ + /* old mountpoint will be dropped when we can do that */ + mnt->mnt_ex_mountpoint = mnt->mnt_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 = dget(mp->m_dentry); + child_mnt->mnt_parent = mnt; + child_mnt->mnt_mp = mp; + hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list); +} + +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); +} + +/* + * vfsmount lock must be held for write + */ +static void attach_mnt(struct mount *mnt, + struct mount *parent, + struct mountpoint *mp) +{ + mnt_set_mountpoint(parent, mp, mnt); + __attach_mnt(mnt, parent); +} + +void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt) +{ + struct mountpoint *old_mp = mnt->mnt_mp; + struct dentry *old_mountpoint = mnt->mnt_mountpoint; + 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); + + put_mountpoint(old_mp); + + /* + * Safely avoid even the suggestion this code might sleep or + * lock the mount hash by taking advantage of the knowledge that + * mnt_change_mountpoint will not release the final reference + * to a mountpoint. + * + * During mounting, the mount passed in as the parent mount will + * continue to use the old mountpoint and during unmounting, the + * old mountpoint will continue to exist until namespace_unlock, + * which happens well after mnt_change_mountpoint. + */ + spin_lock(&old_mountpoint->d_lock); + old_mountpoint->d_lockref.count--; + spin_unlock(&old_mountpoint->d_lock); + + 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; +} + +struct vfsmount * +vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void *data) +{ + struct mount *mnt; + struct dentry *root; + + if (!type) + return ERR_PTR(-ENODEV); + + mnt = alloc_vfsmnt(name); + if (!mnt) + return ERR_PTR(-ENOMEM); + + if (flags & SB_KERNMOUNT) + mnt->mnt.mnt_flags = MNT_INTERNAL; + + root = mount_fs(type, flags, name, data); + if (IS_ERR(root)) { + mnt_free_id(mnt); + free_vfsmnt(mnt); + return ERR_CAST(root); + } + + mnt->mnt.mnt_root = root; + mnt->mnt.mnt_sb = root->d_sb; + mnt->mnt_mountpoint = mnt->mnt.mnt_root; + mnt->mnt_parent = mnt; + lock_mount_hash(); + list_add_tail(&mnt->mnt_instance, &root->d_sb->s_mounts); + unlock_mount_hash(); + return &mnt->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); + /* Don't allow unprivileged users to change mount flags */ + if (flag & CL_UNPRIVILEGED) { + mnt->mnt.mnt_flags |= MNT_LOCK_ATIME; + + if (mnt->mnt.mnt_flags & MNT_READONLY) + mnt->mnt.mnt_flags |= MNT_LOCK_READONLY; + + if (mnt->mnt.mnt_flags & MNT_NODEV) + mnt->mnt.mnt_flags |= MNT_LOCK_NODEV; + + if (mnt->mnt.mnt_flags & MNT_NOSUID) + mnt->mnt.mnt_flags |= MNT_LOCK_NOSUID; + + if (mnt->mnt.mnt_flags & MNT_NOEXEC) + mnt->mnt.mnt_flags |= MNT_LOCK_NOEXEC; + } + + /* Don't allow unprivileged users to reveal what is under a mount */ + if ((flag & CL_UNPRIVILEGED) && + (!(flag & CL_EXPIRE) || list_empty(&old->mnt_expire))) + mnt->mnt.mnt_flags |= MNT_LOCKED; + + atomic_inc(&sb->s_active); + 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) +{ + /* + * This 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); + 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) +{ + 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); + if (mnt_get_count(mnt)) { + 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) { + umount_mnt(p); + } + } + unlock_mount_hash(); + + 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, true)) + 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); + +/* path_is_mountpoint() - Check if path is a mount in the current + * namespace. + * + * 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 +/* 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; + + down_read(&namespace_sem); + if (p->cached_event == p->ns->event) { + void *v = p->cached_mount; + if (*pos == p->cached_index) + return v; + if (*pos == p->cached_index + 1) { + v = seq_list_next(v, &p->ns->list, &p->cached_index); + return p->cached_mount = v; + } + } + + p->cached_event = p->ns->event; + p->cached_mount = seq_list_start(&p->ns->list, *pos); + p->cached_index = *pos; + return p->cached_mount; +} + +static void *m_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct proc_mounts *p = m->private; + + p->cached_mount = seq_list_next(v, &p->ns->list, pos); + p->cached_index = *pos; + return p->cached_mount; +} + +static void m_stop(struct seq_file *m, void *v) +{ + up_read(&namespace_sem); +} + +static int m_show(struct seq_file *m, void *v) +{ + struct proc_mounts *p = m->private; + struct mount *r = list_entry(v, struct mount, mnt_list); + return p->show(m, &r->mnt); +} + +const struct seq_operations mounts_op = { + .start = m_start, + .next = m_next, + .stop = m_stop, + .show = m_show, +}; +#endif /* CONFIG_PROC_FS */ + +/** + * may_umount_tree - check if a mount tree is busy + * @mnt: 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 HLIST_HEAD(unmounted); /* protected by namespace_sem */ + +static void namespace_unlock(void) +{ + struct hlist_head head; + + hlist_move_list(&unmounted, &head); + + up_write(&namespace_sem); + + if (likely(hlist_empty(&head))) + return; + + synchronize_rcu(); + + group_pin_kill(&head); +} + +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); + + pin_insert_group(&p->mnt_umount, &p->mnt_parent->mnt, + disconnect ? &unmounted : NULL); + 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); + } +} + +static void shrink_submounts(struct mount *mnt); + +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; + down_write(&sb->s_umount); + if (!sb_rdonly(sb)) + retval = do_remount_sb(sb, SB_RDONLY, NULL, 0); + up_write(&sb->s_umount); + return retval; + } + + 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 (IS_ERR_OR_NULL(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) { + hlist_add_head(&mnt->mnt_umount.s_list, &unmounted); + umount_mnt(mnt); + } + else umount_tree(mnt, UMOUNT_CONNECTED); + } + put_mountpoint(mp); +out_unlock: + unlock_mount_hash(); + namespace_unlock(); +} + +/* + * Is the caller allowed to modify his namespace? + */ +static inline bool may_mount(void) +{ + return ns_capable(current->nsproxy->mnt_ns->user_ns, CAP_SYS_ADMIN); +} + +#ifdef CONFIG_MANDATORY_FILE_LOCKING +static bool may_mandlock(void) +{ + pr_warn_once("======================================================\n" + "WARNING: the mand mount option is being deprecated and\n" + " will be removed in v5.15!\n" + "======================================================\n"); + return capable(CAP_SYS_ADMIN); +} +#else +static inline bool may_mandlock(void) +{ + pr_warn("VFS: \"mand\" mount option not supported"); + return false; +} +#endif + +/* + * Now umount can handle mount points as well as block devices. + * This is important for filesystems which use unnamed block devices. + * + * We now support a flag for forced unmount like the other 'big iron' + * unixes. Our API is identical to OSF/1 to avoid making a mess of AMD + */ + +int ksys_umount(char __user *name, int flags) +{ + struct path path; + struct mount *mnt; + int retval; + int lookup_flags = 0; + + if (flags & ~(MNT_FORCE | MNT_DETACH | MNT_EXPIRE | UMOUNT_NOFOLLOW)) + return -EINVAL; + + if (!may_mount()) + return -EPERM; + + if (!(flags & UMOUNT_NOFOLLOW)) + lookup_flags |= LOOKUP_FOLLOW; + + retval = user_path_mountpoint_at(AT_FDCWD, name, lookup_flags, &path); + if (retval) + goto out; + mnt = real_mount(path.mnt); + retval = -EINVAL; + if (path.dentry != path.mnt->mnt_root) + goto dput_and_out; + if (!check_mnt(mnt)) + goto dput_and_out; + if (mnt->mnt.mnt_flags & MNT_LOCKED) /* Check optimistically */ + goto dput_and_out; + retval = -EPERM; + if (flags & MNT_FORCE && !capable(CAP_SYS_ADMIN)) + goto dput_and_out; + + retval = do_umount(mnt, flags); +dput_and_out: + /* we mustn't call path_put() as that would clear mnt_expiry_mark */ + dput(path.dentry); + mntput_no_expire(mnt); +out: + return retval; +} + +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; +} + +struct mnt_namespace *to_mnt_ns(struct ns_common *ns) +{ + return container_of(ns, struct mnt_namespace, 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); + 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; +} + +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 + * + * This creates a new vfsmount, which will be the clone of @path. The new 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); + + 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 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, old, pending, sum; + struct mount *p; + + for (p = mnt; p; p = next_mnt(p, mnt)) + mounts++; + + old = ns->mounts; + pending = ns->pending_mounts; + sum = old + pending; + if ((old > sum) || + (pending > sum) || + (max < sum) || + (mounts > (max - sum))) + return -ENOSPC; + + ns->pending_mounts = pending + mounts; + return 0; +} + +/* + * @source_mnt : mount tree to be attached + * @nd : place the mount tree @source_mnt is attached + * @parent_nd : if non-null, detach the source_mnt from its parent and + * store the parent mount and mountpoint dentry. + * (done when source_mnt is moved) + * + * 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. + */ +static int attach_recursive_mnt(struct mount *source_mnt, + struct mount *dest_mnt, + struct mountpoint *dest_mp, + struct path *parent_path) +{ + HLIST_HEAD(tree_list); + struct mnt_namespace *ns = dest_mnt->mnt_ns; + struct mountpoint *smp; + struct mount *child, *p; + struct hlist_node *n; + int err; + + /* Preallocate a mountpoint in case the new mounts need + * to be tucked under other mounts. + */ + 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 (!parent_path) { + err = count_mounts(ns, source_mnt); + if (err) + goto out; + } + + 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; + for (p = source_mnt; p; p = next_mnt(p, source_mnt)) + set_mnt_shared(p); + } else { + lock_mount_hash(); + } + if (parent_path) { + detach_mnt(source_mnt, parent_path); + attach_mnt(source_mnt, dest_mnt, dest_mp); + touch_mnt_namespace(source_mnt->mnt_ns); + } 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); + 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; +} + +static struct mountpoint *lock_mount(struct path *path) +{ + struct vfsmount *mnt; + struct dentry *dentry = path->dentry; +retry: + inode_lock(dentry->d_inode); + if (unlikely(cant_mount(dentry))) { + inode_unlock(dentry->d_inode); + return ERR_PTR(-ENOENT); + } + namespace_lock(); + mnt = lookup_mnt(path); + if (likely(!mnt)) { + struct mountpoint *mp = get_mountpoint(dentry); + if (IS_ERR(mp)) { + namespace_unlock(); + inode_unlock(dentry->d_inode); + return mp; + } + return mp; + } + namespace_unlock(); + inode_unlock(path->dentry->d_inode); + path_put(path); + path->mnt = mnt; + dentry = path->dentry = dget(mnt->mnt_root); + goto retry; +} + +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, NULL); +} + +/* + * 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->dentry != path->mnt->mnt_root) + 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; +} + +/* + * do loopback mount. + */ +static int do_loopback(struct path *path, const char *old_name, + int recurse) +{ + struct path old_path; + struct mount *mnt = NULL, *old, *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); + err = PTR_ERR(mp); + if (IS_ERR(mp)) + goto out; + + old = real_mount(old_path.mnt); + parent = real_mount(path->mnt); + + err = -EINVAL; + if (IS_MNT_UNBINDABLE(old)) + goto out2; + + if (!check_mnt(parent)) + goto out2; + + if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations) + goto out2; + + if (!recurse && has_locked_children(old, old_path.dentry)) + goto out2; + + 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)) { + err = PTR_ERR(mnt); + goto out2; + } + + mnt->mnt.mnt_flags &= ~MNT_LOCKED; + + 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 int change_mount_flags(struct vfsmount *mnt, int ms_flags) +{ + int error = 0; + int readonly_request = 0; + + if (ms_flags & MS_RDONLY) + readonly_request = 1; + if (readonly_request == __mnt_is_readonly(mnt)) + return 0; + + if (readonly_request) + error = mnt_make_readonly(real_mount(mnt)); + else + __mnt_unmake_readonly(real_mount(mnt)); + return error; +} + +/* + * 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); + + if (!check_mnt(mnt)) + return -EINVAL; + + if (path->dentry != path->mnt->mnt_root) + return -EINVAL; + + /* Don't allow changing of locked mnt flags. + * + * 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. + */ + if ((mnt->mnt.mnt_flags & MNT_LOCK_READONLY) && + !(mnt_flags & MNT_READONLY)) { + return -EPERM; + } + if ((mnt->mnt.mnt_flags & MNT_LOCK_NODEV) && + !(mnt_flags & MNT_NODEV)) { + return -EPERM; + } + if ((mnt->mnt.mnt_flags & MNT_LOCK_NOSUID) && + !(mnt_flags & MNT_NOSUID)) { + return -EPERM; + } + if ((mnt->mnt.mnt_flags & MNT_LOCK_NOEXEC) && + !(mnt_flags & MNT_NOEXEC)) { + return -EPERM; + } + if ((mnt->mnt.mnt_flags & MNT_LOCK_ATIME) && + ((mnt->mnt.mnt_flags & MNT_ATIME_MASK) != (mnt_flags & MNT_ATIME_MASK))) { + return -EPERM; + } + + err = security_sb_remount(sb, data); + if (err) + return err; + + down_write(&sb->s_umount); + if (ms_flags & MS_BIND) + err = change_mount_flags(path->mnt, ms_flags); + else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN)) + err = -EPERM; + else + err = do_remount_sb(sb, sb_flags, data, 0); + if (!err) { + lock_mount_hash(); + mnt_flags |= mnt->mnt.mnt_flags & ~MNT_USER_SETTABLE_MASK; + mnt->mnt.mnt_flags = mnt_flags; + touch_mnt_namespace(mnt->mnt_ns); + unlock_mount_hash(); + } + up_write(&sb->s_umount); + 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; +} + +static int do_move_mount(struct path *path, const char *old_name) +{ + struct path old_path, parent_path; + struct mount *p; + struct mount *old; + struct mountpoint *mp; + int err; + if (!old_name || !*old_name) + return -EINVAL; + err = kern_path(old_name, LOOKUP_FOLLOW, &old_path); + if (err) + return err; + + mp = lock_mount(path); + err = PTR_ERR(mp); + if (IS_ERR(mp)) + goto out; + + old = real_mount(old_path.mnt); + p = real_mount(path->mnt); + + err = -EINVAL; + if (!check_mnt(p) || !check_mnt(old)) + goto out1; + + if (old->mnt.mnt_flags & MNT_LOCKED) + goto out1; + + err = -EINVAL; + if (old_path.dentry != old_path.mnt->mnt_root) + goto out1; + + if (!mnt_has_parent(old)) + goto out1; + + if (d_is_dir(path->dentry) != + d_is_dir(old_path.dentry)) + goto out1; + /* + * Don't move a mount residing in a shared parent. + */ + if (IS_MNT_SHARED(old->mnt_parent)) + goto out1; + /* + * 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 out1; + err = -ELOOP; + for (; mnt_has_parent(p); p = p->mnt_parent) + if (p == old) + goto out1; + + err = attach_recursive_mnt(old, real_mount(path->mnt), mp, &parent_path); + if (err) + goto out1; + + /* if the mount is moved, it should no longer be expire + * automatically */ + list_del_init(&old->mnt_expire); +out1: + unlock_mount(mp); +out: + if (!err) + path_put(&parent_path); + path_put(&old_path); + return err; +} + +static struct vfsmount *fs_set_subtype(struct vfsmount *mnt, const char *fstype) +{ + int err; + const char *subtype = strchr(fstype, '.'); + if (subtype) { + subtype++; + err = -EINVAL; + if (!subtype[0]) + goto err; + } else + subtype = ""; + + mnt->mnt_sb->s_subtype = kstrdup(subtype, GFP_KERNEL); + err = -ENOMEM; + if (!mnt->mnt_sb->s_subtype) + goto err; + return mnt; + + err: + mntput(mnt); + return ERR_PTR(err); +} + +/* + * add a mount into a namespace's mount tree + */ +static int do_add_mount(struct mount *newmnt, struct path *path, int mnt_flags) +{ + struct mountpoint *mp; + struct mount *parent; + int err; + + mnt_flags &= ~MNT_INTERNAL_FLAGS; + + mp = lock_mount(path); + if (IS_ERR(mp)) + return PTR_ERR(mp); + + parent = real_mount(path->mnt); + err = -EINVAL; + if (unlikely(!check_mnt(parent))) { + /* that's acceptable only for automounts done in private ns */ + if (!(mnt_flags & MNT_SHRINKABLE)) + goto unlock; + /* ... and for those we'd better have mountpoint still alive */ + if (!parent->mnt_ns) + goto unlock; + } + + /* Refuse the same filesystem on the same mount point */ + err = -EBUSY; + if (path->mnt->mnt_sb == newmnt->mnt.mnt_sb && + path->mnt->mnt_root == path->dentry) + goto unlock; + + err = -EINVAL; + if (d_is_symlink(newmnt->mnt.mnt_root)) + goto unlock; + + newmnt->mnt.mnt_flags = mnt_flags; + err = graft_tree(newmnt, parent, mp); + +unlock: + unlock_mount(mp); + return err; +} + +static bool mount_too_revealing(struct vfsmount *mnt, int *new_mnt_flags); + +/* + * 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 vfsmount *mnt; + int err; + + if (!fstype) + return -EINVAL; + + type = get_fs_type(fstype); + if (!type) + return -ENODEV; + + mnt = vfs_kern_mount(type, sb_flags, name, data); + if (!IS_ERR(mnt) && (type->fs_flags & FS_HAS_SUBTYPE)) { + down_write(&mnt->mnt_sb->s_umount); + if (!mnt->mnt_sb->s_subtype) + mnt = fs_set_subtype(mnt, fstype); + up_write(&mnt->mnt_sb->s_umount); + } + + put_filesystem(type); + if (IS_ERR(mnt)) + return PTR_ERR(mnt); + + if (mount_too_revealing(mnt, &mnt_flags)) { + mntput(mnt); + return -EPERM; + } + + err = do_add_mount(real_mount(mnt), path, mnt_flags); + if (err) + mntput(mnt); + return err; +} + +int finish_automount(struct vfsmount *m, struct path *path) +{ + struct mount *mnt = real_mount(m); + int err; + /* 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 == path->dentry) { + err = -ELOOP; + goto fail; + } + + err = do_add_mount(mnt, path, path->mnt->mnt_flags | MNT_SHRINKABLE); + if (!err) + return 0; +fail: + /* 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); + } + } +} + +/* + * Some copy_from_user() implementations do not return the exact number of + * bytes remaining to copy on a fault. But copy_mount_options() requires that. + * Note that this function differs from copy_from_user() in that it will oops + * on bad values of `to', rather than returning a short copy. + */ +static long exact_copy_from_user(void *to, const void __user * from, + unsigned long n) +{ + char *t = to; + const char __user *f = from; + char c; + + if (!access_ok(VERIFY_READ, from, n)) + return n; + + while (n) { + if (__get_user(c, f)) { + memset(t, 0, n); + break; + } + *t++ = c; + f++; + n--; + } + return n; +} + +void *copy_mount_options(const void __user * data) +{ + int i; + unsigned long size; + char *copy; + + if (!data) + return NULL; + + copy = kmalloc(PAGE_SIZE, GFP_KERNEL); + if (!copy) + return ERR_PTR(-ENOMEM); + + /* We only care that *some* data at the address the user + * gave us is valid. Just in case, we'll zero + * the remainder of the page. + */ + /* copy_from_user cannot cross TASK_SIZE ! */ + size = TASK_SIZE - (unsigned long)data; + if (size > PAGE_SIZE) + size = PAGE_SIZE; + + i = size - exact_copy_from_user(copy, data, size); + if (!i) { + kfree(copy); + return ERR_PTR(-EFAULT); + } + if (i != PAGE_SIZE) + memset(copy + i, 0, PAGE_SIZE - i); + return copy; +} + +char *copy_mount_string(const void __user *data) +{ + return data ? strndup_user(data, PAGE_SIZE) : 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. + */ +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; + unsigned int mnt_flags = 0, sb_flags; + int retval = 0; + + /* 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; + + /* ... and get the mountpoint */ + retval = user_path(dir_name, &path); + if (retval) + return retval; + + retval = security_sb_mount(dev_name, &path, + type_page, flags, data_page); + if (!retval && !may_mount()) + retval = -EPERM; + if (!retval && (flags & SB_MANDLOCK) && !may_mandlock()) + retval = -EPERM; + if (retval) + goto dput_out; + + /* 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; + + /* 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) + retval = do_remount(&path, flags, sb_flags, mnt_flags, + data_page); + else if (flags & MS_BIND) + retval = do_loopback(&path, dev_name, flags & MS_REC); + else if (flags & (MS_SHARED | MS_PRIVATE | MS_SLAVE | MS_UNBINDABLE)) + retval = do_change_type(&path, flags); + else if (flags & MS_MOVE) + retval = do_move_mount(&path, dev_name); + else + retval = do_new_mount(&path, type_page, sb_flags, mnt_flags, + dev_name, data_page); +dput_out: + path_put(&path); + return retval; +} + +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) +{ + 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) +{ + struct mnt_namespace *new_ns; + struct ucounts *ucounts; + int ret; + + ucounts = inc_mnt_namespaces(user_ns); + if (!ucounts) + return ERR_PTR(-ENOSPC); + + new_ns = kmalloc(sizeof(struct mnt_namespace), GFP_KERNEL); + if (!new_ns) { + dec_mnt_namespaces(ucounts); + return ERR_PTR(-ENOMEM); + } + 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; + new_ns->seq = atomic64_add_return(1, &mnt_ns_seq); + atomic_set(&new_ns->count, 1); + new_ns->root = NULL; + INIT_LIST_HEAD(&new_ns->list); + init_waitqueue_head(&new_ns->poll); + new_ns->event = 0; + new_ns->user_ns = get_user_ns(user_ns); + new_ns->ucounts = ucounts; + new_ns->mounts = 0; + new_ns->pending_mounts = 0; + 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); + 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 | CL_UNPRIVILEGED; + 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); + } + 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; + while (p->mnt.mnt_root != q->mnt.mnt_root) + p = next_mnt(p, old); + } + namespace_unlock(); + + if (rootmnt) + mntput(rootmnt); + if (pwdmnt) + mntput(pwdmnt); + + return new_ns; +} + +/** + * create_mnt_ns - creates a private namespace and adds a root filesystem + * @mnt: pointer to the new root filesystem mountpoint + */ +static struct mnt_namespace *create_mnt_ns(struct vfsmount *m) +{ + struct mnt_namespace *new_ns = alloc_mnt_ns(&init_user_ns); + if (!IS_ERR(new_ns)) { + struct mount *mnt = real_mount(m); + mnt->mnt_ns = new_ns; + new_ns->root = mnt; + new_ns->mounts++; + list_add(&mnt->mnt_list, &new_ns->list); + } else { + mntput(m); + } + return new_ns; +} + +struct dentry *mount_subtree(struct vfsmount *mnt, const char *name) +{ + struct mnt_namespace *ns; + struct super_block *s; + struct path path; + int err; + + ns = create_mnt_ns(mnt); + if (IS_ERR(ns)) + return ERR_CAST(ns); + + err = vfs_path_lookup(mnt->mnt_root, mnt, + 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); + +int ksys_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; +} + +SYSCALL_DEFINE5(mount, char __user *, dev_name, char __user *, dir_name, + char __user *, type, unsigned long, flags, void __user *, data) +{ + return ksys_mount(dev_name, dir_name, type, flags, data); +} + +/* + * 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.txt 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, parent_path, root_parent, root; + struct mount *new_mnt, *root_mnt, *old_mnt; + struct mountpoint *old_mp, *root_mp; + int error; + + if (!may_mount()) + return -EPERM; + + error = user_path_dir(new_root, &new); + if (error) + goto out0; + + error = user_path_dir(put_old, &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); + if (IS_MNT_SHARED(old_mnt) || + IS_MNT_SHARED(new_mnt->mnt_parent) || + IS_MNT_SHARED(root_mnt->mnt_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 (root.mnt->mnt_root != root.dentry) + goto out4; /* not a mountpoint */ + if (!mnt_has_parent(root_mnt)) + goto out4; /* not attached */ + root_mp = root_mnt->mnt_mp; + if (new.mnt->mnt_root != new.dentry) + 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(); + root_mp->m_count++; /* pin it so it won't go away */ + detach_mnt(new_mnt, &parent_path); + detach_mnt(root_mnt, &root_parent); + 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); + /* mount new_root on / */ + attach_mnt(new_mnt, real_mount(root_parent.mnt), root_mp); + 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) { + path_put(&root_parent); + path_put(&parent_path); + } +out3: + path_put(&root); +out2: + path_put(&old); +out1: + path_put(&new); +out0: + return error; +} + +static void __init init_mount_tree(void) +{ + struct vfsmount *mnt; + struct mnt_namespace *ns; + struct path root; + struct file_system_type *type; + + type = get_fs_type("rootfs"); + if (!type) + panic("Can't find rootfs type"); + mnt = vfs_kern_mount(type, 0, "rootfs", NULL); + put_filesystem(type); + if (IS_ERR(mnt)) + panic("Can't create rootfs"); + + ns = create_mnt_ns(mnt); + if (IS_ERR(ns)) + panic("Can't allocate initial namespace"); + + 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, 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__); + init_rootfs(); + init_mount_tree(); +} + +void put_mnt_ns(struct mnt_namespace *ns) +{ + if (!atomic_dec_and_test(&ns->count)) + return; + drop_collected_mounts(&ns->root->mnt); + free_mnt_ns(ns); +} + +struct vfsmount *kern_mount_data(struct file_system_type *type, void *data) +{ + struct vfsmount *mnt; + mnt = vfs_kern_mount(type, SB_KERNMOUNT, type->name, data); + 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_data); + +void kern_unmount(struct vfsmount *mnt) +{ + /* release long term mount so mount point can be released */ + if (!IS_ERR_OR_NULL(mnt)) { + real_mount(mnt)->mnt_ns = NULL; + synchronize_rcu(); /* yecchhh... */ + mntput(mnt); + } +} +EXPORT_SYMBOL(kern_unmount); + +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, struct vfsmount *new, + int *new_mnt_flags) +{ + int new_flags = *new_mnt_flags; + struct mount *mnt; + bool visible = false; + + down_read(&namespace_sem); + list_for_each_entry(mnt, &ns->list, mnt_list) { + struct mount *child; + int mnt_flags; + + if (mnt->mnt.mnt_sb->s_type != new->mnt_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: + up_read(&namespace_sem); + return visible; +} + +static bool mount_too_revealing(struct vfsmount *mnt, 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 = mnt->mnt_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, mnt, 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 nsproxy *nsproxy, struct ns_common *ns) +{ + struct fs_struct *fs = current->fs; + struct mnt_namespace *mnt_ns = to_mnt_ns(ns), *old_mnt_ns; + struct path root; + int err; + + if (!ns_capable(mnt_ns->user_ns, CAP_SYS_ADMIN) || + !ns_capable(current_user_ns(), CAP_SYS_CHROOT) || + !ns_capable(current_user_ns(), CAP_SYS_ADMIN)) + return -EPERM; + + 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, +}; |