do_move_mount(): fix an unsafe use of is_anon_ns()

What triggers it is a race between mount --move and umount -l of the source; we should reject it (the source is parentless *and* not the root of anon namespace at that), but the check for namespace being an anon one is broken in that case - is_anon_ns() needs ns to be non-NULL. Better fixed here than in is_anon_ns(), since the rest of the callers is guaranteed to get a non-NULL argument... Reported-by: [email protected] Signed-off-by: Al Viro <[email protected]>
berg · May 9, 2019 · 05883ee · 05883ee
1 parent 80f2321
commit 05883ee
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/fs/namespace.c b/fs/namespace.c
@@ -2599,7 +2599,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
 	if (attached && !check_mnt(old))
 		goto out;
 
-	if (!attached && !is_anon_ns(ns))
+	if (!attached && !(ns && is_anon_ns(ns)))
 		goto out;
 
 	if (old->mnt.mnt_flags & MNT_LOCKED)