mount_is_ancestor(p1, p2) returns true iff there is a possibly
empty ancestry chain from p1 to p2.
Convert the open-coded checks. Unlike those open-coded variants
it does not depend upon p1 not being root...
Signed-off-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
---
fs/namespace.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index 5eeb17c39fcb..b60cb35aa59c 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3491,6 +3491,17 @@ static inline bool path_overmounted(const struct path *path)
return unlikely(!no_child);
}
+/*
+ * Check if there is a possibly empty chain of descent from p1 to p2.
+ * Locks: namespace_sem (shared) or mount_lock (read_seqlock_excl).
+ */
+static bool mount_is_ancestor(const struct mount *p1, const struct mount *p2)
+{
+ while (p2 != p1 && mnt_has_parent(p2))
+ p2 = p2->mnt_parent;
+ return p2 == p1;
+}
+
/**
* can_move_mount_beneath - check that we can mount beneath the top mount
* @from: mount to mount beneath
@@ -3542,9 +3553,8 @@ static int can_move_mount_beneath(const struct path *from,
if (parent_mnt_to == current->nsproxy->mnt_ns->root)
return -EINVAL;
- for (struct mount *p = mnt_from; mnt_has_parent(p); p = p->mnt_parent)
- if (p == mnt_to)
- return -EINVAL;
+ if (mount_is_ancestor(mnt_to, mnt_from))
+ return -EINVAL;
/*
* If the parent mount propagates to the child mount this would
@@ -3713,9 +3723,8 @@ static int do_move_mount(struct path *old_path,
err = -ELOOP;
if (!check_for_nsfs_mounts(old))
goto out;
- for (; mnt_has_parent(p); p = p->mnt_parent)
- if (p == old)
- goto out;
+ if (mount_is_ancestor(old, p))
+ goto out;
err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp, flags);
if (err)
--
2.39.5
