linux-kernel - Re: [syzbot] [fs?] WARNING: lock held when returning to user space in ns

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Message-Id: <20240718110318.1438-1-hdanton@sina.com>
Date: Thu, 18 Jul 2024 19:03:17 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+dd73570cf9918519e789@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [fs?] WARNING: lock held when returning to user space in ns_ioctl

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:
--