[PATCH] fs: don't try and remove empty rbtree node

[Christian Brauner <brauner@kernel.org>]

When copying a namespace we won't have added the new copy into the
namespace rbtree until after the copy succeeded. Calling free_mnt_ns()
will try to remove the copy from the rbtree which is invalid. Simply
free the namespace skeleton directly.

Fixes: 1901c92497bd ("fs: keep an index of current mount namespaces")
Cc: stable@vger.kernel.org # v6.11+
Reported-by: Brad Spengler <spender@grsecurity.net>
Tested-by: Brad Spengler <spender@grsecurity.net>
Suggested-by: Brad Spengler <spender@grsecurity.net>
Signed-off-by: Christian Brauner <brauner@kernel.org>
---
In vfs.fixes unless I hear objections.
---
 fs/namespace.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/fs/namespace.c b/fs/namespace.c
index 93c377816d75..d26f5e6d2ca3 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3944,7 +3944,9 @@ struct mnt_namespace *copy_mnt_ns(unsigned long flags, struct mnt_namespace *ns,
 	new = copy_tree(old, old->mnt.mnt_root, copy_flags);
 	if (IS_ERR(new)) {
 		namespace_unlock();
-		free_mnt_ns(new_ns);
+		ns_free_inum(&new_ns->ns);
+		dec_mnt_namespaces(new_ns->ucounts);
+		mnt_ns_release(new_ns);
 		return ERR_CAST(new);
 	}
 	if (user_ns != ns->user_ns) {
-- 
2.45.2