linux-kernel - Re: [syzbot] [overlayfs?] WARNING in fast

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Message-ID: <20251129215828.9544-1-hdanton@sina.com>
Date: Sun, 30 Nov 2025 05:58:27 +0800
From: Hillf Danton <hdanton@...a.com>
To: syzbot <syzbot+b74150fd2ef40e716ca2@...kaller.appspotmail.com>
Cc: linux-kernel@...r.kernel.org,
	syzkaller-bugs@...glegroups.com
Subject: Re: [syzbot] [overlayfs?] WARNING in fast_dput

> Date: Sat, 29 Nov 2025 05:05:23 -0800	[thread overview]
> Hello,
> 
> syzbot found the following issue on:
> 
> HEAD commit:    7d31f578f323 Add linux-next specific files for 20251128
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14db5f42580000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=6336d8e94a7c517d
> dashboard link: https://syzkaller.appspot.com/bug?extid=b74150fd2ef40e716ca2
> compiler:       Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
> syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1780a112580000
> C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=10f6be92580000

#syz test

--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -1224,9 +1224,9 @@ int ovl_lock_rename_workdir(struct dentr
 		goto err;
 	if (trap)
 		goto err_unlock;
-	if (work && work->d_parent != workdir)
+	if (work && (work->d_parent != workdir || d_unhashed(work)))
 		goto err_unlock;
-	if (upper && upper->d_parent != upperdir)
+	if (upper && (upper->d_parent != upperdir || d_unhashed(work)))
 		goto err_unlock;
 
 	return 0;
--