From 05883eee857eab4693e7d13ebab06716475c5754 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Thu, 9 May 2019 02:32:28 -0400 Subject: [PATCH] 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: syzbot+494c7ddf66acac0ad747@syzkaller.appspotmail.com Signed-off-by: Al Viro --- fs/namespace.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/namespace.c b/fs/namespace.c index 3357c3d65475..ffb13f0562b0 100644 --- 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)