[syzbot] WARNING in __brelse

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 46452d3786a8 Merge tag 'sound-6.0-rc8' of git://git.kernel..
git tree: upstream
console+strace: https://syzkaller.appspot.com/x/log.txt?x=154595ef080000
kernel config: https://syzkaller.appspot.com/x/.config?x=755695d26ad09807
dashboard link: https://syzkaller.appspot.com/bug?extid=7902cd7684bc35306224
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=127543c4880000
C reproducer: https://syzkaller.appspot.com/x/repro.c?x=1740b138880000

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+7902cd...@syzkaller.appspotmail.com

------------[ cut here ]------------
VFS: brelse: Trying to free free buffer
WARNING: CPU: 0 PID: 3604 at fs/buffer.c:1145 __brelse fs/buffer.c:1145 [inline]
WARNING: CPU: 0 PID: 3604 at fs/buffer.c:1145 __brelse+0x67/0xa0 fs/buffer.c:1139
Modules linked in:
CPU: 0 PID: 3604 Comm: syz-executor576 Not tainted 6.0.0-rc7-syzkaller-00042-g46452d3786a8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/26/2022
RIP: 0010:__brelse fs/buffer.c:1145 [inline]
RIP: 0010:__brelse+0x67/0xa0 fs/buffer.c:1139
Code: 7c 04 84 d2 75 4e 44 8b 63 60 31 ff 44 89 e6 e8 8f 57 95 ff 45 85 e4 75 1c e8 c5 5a 95 ff 48 c7 c7 00 93 fc 89 e8 5b 6f 54 07 <0f> 0b 5b 5d 41 5c e9 ae 5a 95 ff e8 a9 5a 95 ff be 04 00 00 00 48
RSP: 0018:ffffc9000379fbb0 EFLAGS: 00010086
RAX: 0000000000000000 RBX: ffff8880747e4bc8 RCX: 0000000000000000
RDX: ffff888024c61d80 RSI: ffffffff8161f2a8 RDI: fffff520006f3f68
RBP: ffff8880747e4c28 R08: 0000000000000005 R09: 0000000000000000
R10: 0000000080000002 R11: 0000000000000000 R12: 0000000000000000
R13: dffffc0000000000 R14: ffff8880b9a35f80 R15: 0000000000000008
FS: 0000555556bf6300(0000) GS:ffff8880b9a00000(0000) knlGS:0000000000000000
CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033
CR2: 00007ff88e983290 CR3: 00000000715c2000 CR4: 0000000000350ef0
Call Trace:
<TASK>
brelse include/linux/buffer_head.h:327 [inline]
__invalidate_bh_lrus fs/buffer.c:1391 [inline]
invalidate_bh_lru+0x99/0x150 fs/buffer.c:1404
smp_call_function_many_cond+0x10e2/0x1430 kernel/smp.c:979
on_each_cpu_cond_mask+0x56/0xa0 kernel/smp.c:1154
kill_bdev block/bdev.c:74 [inline]
blkdev_flush_mapping+0x136/0x2f0 block/bdev.c:661
blkdev_put_whole+0xd1/0xf0 block/bdev.c:692
blkdev_put+0x226/0x770 block/bdev.c:952
deactivate_locked_super+0x94/0x160 fs/super.c:332
deactivate_super+0xad/0xd0 fs/super.c:363
cleanup_mnt+0x2ae/0x3d0 fs/namespace.c:1186
task_work_run+0xdd/0x1a0 kernel/task_work.c:177
ptrace_notify+0x114/0x140 kernel/signal.c:2353
ptrace_report_syscall include/linux/ptrace.h:420 [inline]
ptrace_report_syscall_exit include/linux/ptrace.h:482 [inline]
syscall_exit_work kernel/entry/common.c:249 [inline]
syscall_exit_to_user_mode_prepare+0x129/0x280 kernel/entry/common.c:276
__syscall_exit_to_user_mode_work kernel/entry/common.c:281 [inline]
syscall_exit_to_user_mode+0x9/0x50 kernel/entry/common.c:294
do_syscall_64+0x42/0xb0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x63/0xcd
RIP: 0033:0x7ff88e90ec27
Code: 07 00 48 83 c4 08 5b 5d c3 66 2e 0f 1f 84 00 00 00 00 00 c3 66 2e 0f 1f 84 00 00 00 00 00 0f 1f 44 00 00 b8 a6 00 00 00 0f 05 <48> 3d 01 f0 ff ff 73 01 c3 48 c7 c1 c0 ff ff ff f7 d8 64 89 01 48
RSP: 002b:00007ffe36cd2398 EFLAGS: 00000202 ORIG_RAX: 00000000000000a6
RAX: 0000000000000000 RBX: 0000000000000000 RCX: 00007ff88e90ec27
RDX: 00007ffe36cd2459 RSI: 000000000000000a RDI: 00007ffe36cd2450
RBP: 00007ffe36cd2450 R08: 00000000ffffffff R09: 00007ffe36cd2230
R10: 0000555556bf7653 R11: 0000000000000202 R12: 00007ffe36cd34d0
R13: 0000555556bf75f0 R14: 00007ffe36cd23c0 R15: 0000000000000005
</TASK>


---
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[Al Viro]

On Wed, Sep 28, 2022 at 01:43:39PM -0700, syzbot wrote:
> Hello,
>
> syzbot found the following issue on:
>
> HEAD commit: 46452d3786a8 Merge tag 'sound-6.0-rc8' of git://git.kernel..
> git tree: upstream
> console+strace: https://syzkaller.appspot.com/x/log.txt?x=154595ef080000
> kernel config: https://syzkaller.appspot.com/x/.config?x=755695d26ad09807
> dashboard link: https://syzkaller.appspot.com/bug?extid=7902cd7684bc35306224
> 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=127543c4880000

For crying out loud... Seeing that it has

syz_mount_image$udf(

in it and seeing that MAINTAINERS has

UDF FILESYSTEM
M: Jan Kara <ja...@suse.com>
S: Maintained
F: Documentation/filesystems/udf.rst
F: fs/udf/

which word is missing in Subject and which mail is missing in Cc?

"[syzbot] WARNING in __brelse" says nothing beyond "it's probably about
something that does buffer_head IO". Recepients of that mail have no way
to find which fs is involved without wget of your reproducer and looking
into it (well, that or start a browser, cut'n'paste the URL there, etc.).
You, OTOH, have that information from the very beginning...