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-rw-r--r--fs/namespace.c4732
1 files changed, 4732 insertions, 0 deletions
diff --git a/fs/namespace.c b/fs/namespace.c
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index 000000000..29a8d90dd
--- /dev/null
+++ b/fs/namespace.c
@@ -0,0 +1,4732 @@
+// 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;
+};
+
+/* /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_userns = &init_user_ns;
+ }
+ 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 (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();
+ 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();
+ }
+ }
+ /*
+ * 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_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->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)
+{
+ struct user_namespace *mnt_userns;
+
+ mnt_userns = mnt_user_ns(&mnt->mnt);
+ if (!initial_idmapping(mnt_userns))
+ put_user_ns(mnt_userns);
+ 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;
+}
+
+/*
+ * 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;
+}
+
+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);
+}
+
+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 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);
+ 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;
+ struct user_namespace *fs_userns;
+
+ 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;
+
+ fs_userns = mnt->mnt.mnt_sb->s_user_ns;
+ if (!initial_idmapping(fs_userns))
+ mnt->mnt.mnt_userns = get_user_ns(fs_userns);
+
+ 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_userns = mnt_user_ns(&old->mnt);
+ if (!initial_idmapping(mnt->mnt.mnt_userns))
+ mnt->mnt.mnt_userns = get_user_ns(mnt->mnt.mnt_userns);
+ 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);
+
+/**
+ * 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);
+}
+
+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->dentry != path->mnt->mnt_root)
+ 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);
+ 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;
+}
+
+/*
+ * @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,
+ bool moving)
+{
+ struct user_namespace *user_ns = current->nsproxy->mnt_ns->user_ns;
+ 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 (!moving) {
+ 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 (moving) {
+ unhash_mnt(source_mnt);
+ attach_mnt(source_mnt, dest_mnt, dest_mp);
+ 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);
+ }
+ 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;
+}
+
+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, false);
+}
+
+/*
+ * 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;
+}
+
+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);
+ struct tm tm;
+
+ time64_to_tm(sb->s_time_max, 0, &tm);
+
+ pr_warn("%s filesystem being %s at %s supports timestamps until %04ld (0x%llx)\n",
+ sb->s_type->name,
+ is_mounted(mnt) ? "remounted" : "mounted",
+ mntpath,
+ tm.tm_year+1900, (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->dentry != mnt->mnt.mnt_root)
+ 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->dentry != path->mnt->mnt_root)
+ 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 (from_path->dentry != from_path->mnt->mnt_root)
+ goto out;
+ if (to_path->dentry != to_path->mnt->mnt_root)
+ 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;
+}
+
+static int do_move_mount(struct path *old_path, struct path *new_path)
+{
+ struct mnt_namespace *ns;
+ struct mount *p;
+ struct mount *old;
+ struct mount *parent;
+ struct mountpoint *mp, *old_mp;
+ int err;
+ bool attached;
+
+ mp = lock_mount(new_path);
+ 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);
+ 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 (old_path->dentry != old_path->mnt->mnt_root)
+ 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;
+ /*
+ * 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,
+ attached);
+ 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);
+ 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->mnt->mnt_root == path->dentry)
+ 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;
+ }
+ rcu_read_lock();
+ if (unlikely(__lookup_mnt(path->mnt, dentry))) {
+ rcu_read_unlock();
+ err = 0;
+ goto discard_locked;
+ }
+ rcu_read_unlock();
+ 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;
+ 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;
+}
+
+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 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);
+
+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 (root.mnt->mnt_root != root.dentry)
+ goto out4; /* not a mountpoint */
+ if (!mnt_has_parent(root_mnt))
+ goto out4; /* not attached */
+ 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();
+ 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);
+ /* mount new_root on / */
+ attach_mnt(new_mnt, root_parent, root_mp);
+ 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_userns)
+ 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 (kattr->mnt_userns == fs_userns)
+ 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_userns;
+}
+
+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)
+{
+ struct user_namespace *mnt_userns, *old_mnt_userns;
+
+ if (!kattr->mnt_userns)
+ return;
+
+ /*
+ * We're the only ones able to change the mount's idmapping. So
+ * mnt->mnt.mnt_userns is stable and we can retrieve it directly.
+ */
+ old_mnt_userns = mnt->mnt.mnt_userns;
+
+ mnt_userns = get_user_ns(kattr->mnt_userns);
+ /* Pairs with smp_load_acquire() in mnt_user_ns(). */
+ smp_store_release(&mnt->mnt.mnt_userns, mnt_userns);
+
+ /*
+ * If this is an idmapped filesystem drop the reference we've taken
+ * in vfs_create_mount() before.
+ */
+ if (!initial_idmapping(old_mnt_userns))
+ put_user_ns(old_mnt_userns);
+}
+
+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->dentry != mnt->mnt.mnt_root)
+ return -EINVAL;
+
+ 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 file *file;
+
+ 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;
+
+ file = fget(attr->userns_fd);
+ if (!file)
+ return -EBADF;
+
+ if (!proc_ns_file(file)) {
+ err = -EINVAL;
+ goto out_fput;
+ }
+
+ ns = get_proc_ns(file_inode(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 (initial_idmapping(mnt_userns)) {
+ 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:
+ fput(file);
+ 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;
+}
+
+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_OR_NULL(mnt)) {
+ real_mount(mnt)->mnt_ns = NULL;
+ 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++)
+ if (mnt[i])
+ real_mount(mnt[i])->mnt_ns = NULL;
+ 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 = &current->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 */