From: Christian Brauner <brauner@kernel.org>
Date: Fri, 21 Feb 2025 13:13:02 +0000 (+0100)
Subject: fs: add assert for move_mount()
X-Git-Tag: v6.15-rc1~244^2~3^2~13
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=043bc81efbfc5580ecd9da76118722649205f30a;p=thirdparty%2Fkernel%2Flinux.git

fs: add assert for move_mount()

After we've attached a detached mount tree the anonymous mount namespace
must be empty. Add an assert and make this assumption explicit.

Link: https://lore.kernel.org/r/20250221-brauner-open_tree-v1-3-dbcfcb98c676@kernel.org
Signed-off-by: Christian Brauner <brauner@kernel.org>
---

diff --git a/fs/namespace.c b/fs/namespace.c
index 8ca28737f4ee8..c9670a198b507 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -3423,10 +3423,13 @@ static int do_move_mount(struct path *old_path, struct path *new_path,
 out:
 	unlock_mount(mp);
 	if (!err) {
-		if (attached)
+		if (attached) {
 			mntput_no_expire(parent);
-		else
+		} else {
+			/* Make sure we notice when we leak mounts. */
+			VFS_WARN_ON_ONCE(!mnt_ns_empty(ns));
 			free_mnt_ns(ns);
+		}
 	}
 	return err;
 }