On 10/23/21 22:35, syzbot wrote:
Hello,
syzbot found the following issue on:
HEAD commit: cf6c9d12750c Add linux-next specific files for 20211022
git tree: linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15d3d4c4b00000
kernel config: https://syzkaller.appspot.com/x/.config?x=e694204255ade3a3
dashboard link: https://syzkaller.appspot.com/bug?extid=ace149a75a9a0a399ac7
compiler: gcc (Debian 10.2.1-6) 10.2.1 20210110, GNU ld (GNU Binutils for Debian) 2.35.2
syz repro: https://syzkaller.appspot.com/x/repro.syz?x=17c0530cb00000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1129c952b00000
The issue was bisected to:
commit 411cef6adfb38a5bb6bd9af3941b28198e7fb680
Author: Takashi Iwai <tiwai@xxxxxxx>
Date: Wed Oct 20 16:48:46 2021 +0000
ALSA: mixer: oss: Fix racy access to slots
bisection log: https://syzkaller.appspot.com/x/bisect.txt?x=167f6454b00000
final oops: https://syzkaller.appspot.com/x/report.txt?x=157f6454b00000
console output: https://syzkaller.appspot.com/x/log.txt?x=117f6454b00000
IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+ace149a75a9a0a399ac7@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 411cef6adfb3 ("ALSA: mixer: oss: Fix racy access to slots")
============================================
WARNING: possible recursive locking detected
5.15.0-rc6-next-20211022-syzkaller #0 Not tainted
--------------------------------------------
syz-executor206/6529 is trying to acquire lock:
ffff888021ff09c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:316 [inline]
ffff888021ff09c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_ioctl1+0x630/0x19a0 sound/core/oss/mixer_oss.c:375
but task is already holding lock:
ffff888021ff09c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_set_volume sound/core/oss/mixer_oss.c:300 [inline]
ffff888021ff09c8 (&mixer->reg_mutex){+.+.}-{3:3}, at: snd_mixer_oss_ioctl1+0x4b1/0x19a0 sound/core/oss/mixer_oss.c:375
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&mixer->reg_mutex);
lock(&mixer->reg_mutex);
*** DEADLOCK ***
May be due to missing lock nesting notation
Looks like typo in previous ALSA patch. [1] should fix it
[1]
https://lore.kernel.org/alsa-devel/20211024140315.16704-1-paskripkin@xxxxxxxxx/T/#u
With regards,
Pavel Skripkin
