linux-kernel - Re: [syzbot] [overlayfs?] possible deadlock in iter_file_splice

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Date: Thu, 14 Mar 2024 10:27:11 +0100
From: Miklos Szeredi <miklos@...redi.hu>
To: syzbot <syzbot+e525d9be15a106e48379@...kaller.appspotmail.com>
Cc: amir73il@...il.com, linux-fsdevel@...r.kernel.org, 
	linux-kernel@...r.kernel.org, linux-unionfs@...r.kernel.org, 
	syzkaller-bugs@...glegroups.com, "Rafael J. Wysocki" <rafael@...nel.org>
Subject: Re: [syzbot] [overlayfs?] possible deadlock in iter_file_splice_write (3)

On Thu, 14 Mar 2024 at 00:10, syzbot
<syzbot+e525d9be15a106e48379@...kaller.appspotmail.com> wrote:

> -> #3 (&ovl_i_mutex_dir_key[depth]){++++}-{3:3}:
>        lock_acquire+0x1e3/0x530 kernel/locking/lockdep.c:5754
>        down_read+0xb1/0xa40 kernel/locking/rwsem.c:1526
>        inode_lock_shared include/linux/fs.h:814 [inline]
>        lookup_slow+0x45/0x70 fs/namei.c:1709
>        walk_component+0x2e1/0x410 fs/namei.c:2005
>        lookup_last fs/namei.c:2462 [inline]
>        path_lookupat+0x16f/0x450 fs/namei.c:2486
>        filename_lookup+0x255/0x610 fs/namei.c:2515
>        kern_path+0x35/0x50 fs/namei.c:2623

This is what ultimately closes the locking loop: doing path lookup
(taking directory i_mutex) with kernfs of->mutex held.

#syz dup possible deadlock in seq_read_iter (3)

Thanks,
Miklos