Returns the final (topmost) mount in the chain of overmounts
starting at given mount. Same locking rules as for any mount
tree traversal - either the spinlock side of mount_lock, or
rcu + sample the seqcount side of mount_lock before the call
and recheck afterwards.
Reviewed-by: Christian Brauner <brauner@xxxxxxxxxx>
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/mount.h | 7 +++++++
fs/namespace.c | 9 +++------
2 files changed, 10 insertions(+), 6 deletions(-)
diff --git a/fs/mount.h b/fs/mount.h
index ed8c83ba836a..04d0eadc4c10 100644
--- a/fs/mount.h
+++ b/fs/mount.h
@@ -235,4 +235,11 @@ static inline void mnt_notify_add(struct mount *m)
}
#endif
+static inline struct mount *topmost_overmount(struct mount *m)
+{
+ while (m->overmount)
+ m = m->overmount;
+ return m;
+}
+
struct mnt_namespace *mnt_ns_from_dentry(struct dentry *dentry);
diff --git a/fs/namespace.c b/fs/namespace.c
index 085877bfaa5e..ebecb03972c5 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -2696,10 +2696,9 @@ static int attach_recursive_mnt(struct mount *source_mnt,
child->mnt_mountpoint);
commit_tree(child);
if (q) {
+ struct mount *r = topmost_overmount(child);
struct mountpoint *mp = root.mp;
- struct mount *r = child;
- while (unlikely(r->overmount))
- r = r->overmount;
+
if (unlikely(shorter) && child != source_mnt)
mp = shorter;
mnt_change_mountpoint(r, mp, q);
@@ -6171,9 +6170,7 @@ bool current_chrooted(void)
guard(mount_locked_reader)();
- root = current->nsproxy->mnt_ns->root;
- while (unlikely(root->overmount))
- root = root->overmount;
+ root = topmost_overmount(current->nsproxy->mnt_ns->root);
return fs_root.mnt != &root->mnt || !path_mounted(&fs_root);
}
--
2.47.2
