Re: [syzbot] [fs?] WARNING: lock held when returning to user space in ns_ioctl

[Hillf Danton]

On Wed, 17 Jul 2024 18:31:24 -0700
> syzbot found the following issue on:
> 
> HEAD commit:    51835949dda3 Merge tag 'net-next-6.11' of git://git.kernel..
> git tree:       upstream
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=15ef5b4e980000

#syz test https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git  51835949dda3

--- x/fs/nsfs.c
+++ y/fs/nsfs.c
@@ -188,8 +188,10 @@ static long ns_ioctl(struct file *filp,
 			tsk = find_task_by_vpid(arg);
 		else
 			tsk = find_task_by_pid_ns(arg, pid_ns);
-		if (!tsk)
+		if (!tsk) {
+			rcu_read_unlock();
 			break;
+		}
 
 		switch (ioctl) {
 		case NS_GET_PID_FROM_PIDNS:
--