mnt_dec_writers(real_mount(mnt));
preempt_enable();
}
+EXPORT_SYMBOL_GPL(__mnt_drop_write);
/**
* mnt_drop_write - give up write access to a mount
return NULL;
}
-/*
- * find the last mount at @dentry on vfsmount @mnt.
- * mount_lock must be held.
- */
-struct mount *__lookup_mnt_last(struct vfsmount *mnt, struct dentry *dentry)
-{
- struct mount *p, *res = NULL;
- p = __lookup_mnt(mnt, dentry);
- if (!p)
- goto out;
- if (!(p->mnt.mnt_flags & MNT_UMOUNT))
- res = p;
- hlist_for_each_entry_continue(p, mnt_hash) {
- if (&p->mnt_parent->mnt != mnt || p->mnt_mountpoint != dentry)
- break;
- if (!(p->mnt.mnt_flags & MNT_UMOUNT))
- res = p;
- }
-out:
- return res;
-}
-
/*
* lookup_mnt - Return the first child mount mounted at path
*
return NULL;
}
-static struct mountpoint *new_mountpoint(struct dentry *dentry)
+static struct mountpoint *get_mountpoint(struct dentry *dentry)
{
- struct hlist_head *chain = mp_hash(dentry);
- struct mountpoint *mp;
+ struct mountpoint *mp, *new = NULL;
int ret;
- mp = kmalloc(sizeof(struct mountpoint), GFP_KERNEL);
- if (!mp)
+ if (d_mountpoint(dentry)) {
+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);
- if (ret) {
- kfree(mp);
- return ERR_PTR(ret);
- }
- mp->m_dentry = dentry;
- mp->m_count = 1;
- hlist_add_head(&mp->m_hash, chain);
- INIT_HLIST_HEAD(&mp->m_list);
+ /* Someone else set d_mounted? */
+ if (ret == -EBUSY)
+ goto mountpoint;
+
+ /* The dentry is not available as a mountpoint? */
+ mp = ERR_PTR(ret);
+ if (ret)
+ goto done;
+
+ /* Add the new mountpoint to the hash table */
+ read_seqlock_excl(&mount_lock);
+ new->m_dentry = dentry;
+ new->m_count = 1;
+ hlist_add_head(&new->m_hash, mp_hash(dentry));
+ INIT_HLIST_HEAD(&new->m_list);
+ read_sequnlock_excl(&mount_lock);
+
+ mp = new;
+ new = NULL;
+done:
+ kfree(new);
return mp;
}
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
*/
struct mountpoint *mp)
{
mnt_set_mountpoint(parent, mp, mnt);
- hlist_add_head_rcu(&mnt->mnt_hash, m_hash(&parent->mnt, mp->m_dentry));
- list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
+ __attach_mnt(mnt, parent);
}
-static void attach_shadowed(struct mount *mnt,
- struct mount *parent,
- struct mount *shadows)
+void mnt_change_mountpoint(struct mount *parent, struct mountpoint *mp, struct mount *mnt)
{
- if (shadows) {
- hlist_add_behind_rcu(&mnt->mnt_hash, &shadows->mnt_hash);
- list_add(&mnt->mnt_child, &shadows->mnt_child);
- } else {
- hlist_add_head_rcu(&mnt->mnt_hash,
- m_hash(&parent->mnt, mnt->mnt_mountpoint));
- list_add_tail(&mnt->mnt_child, &parent->mnt_mounts);
- }
+ struct mountpoint *old_mp = mnt->mnt_mp;
+ struct dentry *old_mountpoint = mnt->mnt_mountpoint;
+ struct mount *old_parent = mnt->mnt_parent;
+
+ list_del_init(&mnt->mnt_child);
+ hlist_del_init(&mnt->mnt_mp_list);
+ hlist_del_init_rcu(&mnt->mnt_hash);
+
+ attach_mnt(mnt, parent, mp);
+
+ put_mountpoint(old_mp);
+
+ /*
+ * Safely avoid even the suggestion this code might sleep or
+ * lock the mount hash by taking advantage of the knowledge that
+ * mnt_change_mountpoint will not release the final reference
+ * to a mountpoint.
+ *
+ * During mounting, the mount passed in as the parent mount will
+ * continue to use the old mountpoint and during unmounting, the
+ * old mountpoint will continue to exist until namespace_unlock,
+ * which happens well after mnt_change_mountpoint.
+ */
+ spin_lock(&old_mountpoint->d_lock);
+ old_mountpoint->d_lockref.count--;
+ spin_unlock(&old_mountpoint->d_lock);
+
+ mnt_add_count(old_parent, -1);
}
/*
* vfsmount lock must be held for write
*/
-static void commit_tree(struct mount *mnt, struct mount *shadows)
+static void commit_tree(struct mount *mnt)
{
struct mount *parent = mnt->mnt_parent;
struct mount *m;
n->mounts += n->pending_mounts;
n->pending_mounts = 0;
- attach_shadowed(mnt, parent, shadows);
+ __attach_mnt(mnt, parent);
touch_mnt_namespace(n);
}
}
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, MS_SUBMOUNT, name, data);
+}
+EXPORT_SYMBOL_GPL(vfs_submount);
+
static struct mount *clone_mnt(struct mount *old, struct dentry *root,
int flag)
{
* Special case for "unmounting" root ...
* we just try to remount it readonly.
*/
- if (!capable(CAP_SYS_ADMIN))
+ if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
return -EPERM;
down_write(&sb->s_umount);
if (!(sb->s_flags & MS_RDONLY))
struct mount *mnt;
namespace_lock();
+ lock_mount_hash();
mp = lookup_mountpoint(dentry);
if (IS_ERR_OR_NULL(mp))
goto out_unlock;
- lock_mount_hash();
event++;
while (!hlist_empty(&mp->m_list)) {
mnt = hlist_entry(mp->m_list.first, struct mount, mnt_mp_list);
}
else umount_tree(mnt, UMOUNT_CONNECTED);
}
- unlock_mount_hash();
put_mountpoint(mp);
out_unlock:
+ unlock_mount_hash();
namespace_unlock();
}
continue;
for (s = r; s; s = next_mnt(s, r)) {
- struct mount *t = NULL;
if (!(flag & CL_COPY_UNBINDABLE) &&
IS_MNT_UNBINDABLE(s)) {
s = skip_mnt_tree(s);
goto out;
lock_mount_hash();
list_add_tail(&q->mnt_list, &res->mnt_list);
- mnt_set_mountpoint(parent, p->mnt_mp, q);
- if (!list_empty(&parent->mnt_mounts)) {
- t = list_last_entry(&parent->mnt_mounts,
- struct mount, mnt_child);
- if (t->mnt_mp != p->mnt_mp)
- t = NULL;
- }
- attach_shadowed(q, parent, t);
+ attach_mnt(q, parent, p->mnt_mp);
unlock_mount_hash();
}
}
}
return 0;
}
+EXPORT_SYMBOL_GPL(iterate_mounts);
static void cleanup_group_ids(struct mount *mnt, struct mount *end)
{
{
HLIST_HEAD(tree_list);
struct mnt_namespace *ns = dest_mnt->mnt_ns;
+ struct mountpoint *smp;
struct mount *child, *p;
struct hlist_node *n;
int err;
+ /* Preallocate a mountpoint in case the new mounts need
+ * to be tucked under other mounts.
+ */
+ smp = get_mountpoint(source_mnt->mnt.mnt_root);
+ if (IS_ERR(smp))
+ return PTR_ERR(smp);
+
/* Is there space to add these mounts to the mount namespace? */
if (!parent_path) {
err = count_mounts(ns, source_mnt);
touch_mnt_namespace(source_mnt->mnt_ns);
} else {
mnt_set_mountpoint(dest_mnt, dest_mp, source_mnt);
- commit_tree(source_mnt, NULL);
+ 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_last(&child->mnt_parent->mnt,
- child->mnt_mountpoint);
- commit_tree(child, q);
+ q = __lookup_mnt(&child->mnt_parent->mnt,
+ child->mnt_mountpoint);
+ if (q)
+ mnt_change_mountpoint(child, smp, q);
+ commit_tree(child);
}
+ put_mountpoint(smp);
unlock_mount_hash();
return 0;
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;
}
namespace_lock();
mnt = lookup_mnt(path);
if (likely(!mnt)) {
- struct mountpoint *mp = lookup_mountpoint(dentry);
- if (!mp)
- mp = new_mountpoint(dentry);
+ struct mountpoint *mp = get_mountpoint(dentry);
if (IS_ERR(mp)) {
namespace_unlock();
inode_unlock(dentry->d_inode);
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);
}
down_write(&sb->s_umount);
if (flags & MS_BIND)
err = change_mount_flags(path->mnt, flags);
- else if (!capable(CAP_SYS_ADMIN))
+ else if (!ns_capable(sb->s_user_ns, CAP_SYS_ADMIN))
err = -EPERM;
else
err = do_remount_sb(sb, flags, data, 0);
flags &= ~(MS_NOSUID | MS_NOEXEC | MS_NODEV | MS_ACTIVE | MS_BORN |
MS_NOATIME | MS_NODIRATIME | MS_RELATIME| MS_KERNMOUNT |
- MS_STRICTATIME | MS_NOREMOTELOCK);
+ MS_STRICTATIME | MS_NOREMOTELOCK | MS_SUBMOUNT);
if (flags & MS_REMOUNT)
retval = do_remount(&path, flags & ~MS_REMOUNT, mnt_flags,
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);
- put_mountpoint(root_mp);
error = 0;
out4:
unlock_mount(old_mp);
projects / mirror_ubuntu-zesty-kernel.git / blobdiff