Re: linux-next test error: WARNING in snd_pcm_plug_alloc

[Takashi Iwai]

On Thu, 12 Mar 2020 16:47:14 +0100,
syzbot wrote:
> 
> Hello,
> 
> syzbot found the following crash on:
> 
> HEAD commit:    407b0a62 Add linux-next specific files for 20200312
> git tree:       linux-next
> console output: https://syzkaller.appspot.com/x/log.txt?x=14dd6545e00000
> kernel config:  https://syzkaller.appspot.com/x/.config?x=d644875269fc730b
> dashboard link: https://syzkaller.appspot.com/bug?extid=2a59ee7a9831b264f45e
> compiler:       gcc (GCC) 9.0.0 20181231 (experimental)
> 
> Unfortunately, I don't have any reproducer for this crash yet.
> 
> IMPORTANT: if you fix the bug, please add the following tag to the commit:
> Reported-by: syzbot+2a59ee7a9831b264f45e@xxxxxxxxxxxxxxxxxxxxxxxxx
> 
> ------------[ cut here ]------------
> WARNING: CPU: 0 PID: 8559 at sound/core/oss/pcm_plugin.c:126 snd_pcm_plug_alloc+0x29a/0x330 sound/core/oss/pcm_plugin.c:126

This looks like rather a spurious WARNING(), we can get rid of
snd_BUG_ON() usage there, as the condition can be triggered by the
user-space parameter change.


Takashi

> Kernel panic - not syncing: panic_on_warn set ...
> CPU: 0 PID: 8559 Comm: syz-fuzzer Not tainted 5.6.0-rc5-next-20200312-syzkaller #0
> Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
> Call Trace:
>  __dump_stack lib/dump_stack.c:77 [inline]
>  dump_stack+0x188/0x20d lib/dump_stack.c:118
>  panic+0x2e3/0x75c kernel/panic.c:221
>  __warn.cold+0x2f/0x35 kernel/panic.c:582
>  report_bug+0x27b/0x2f0 lib/bug.c:195
>  fixup_bug arch/x86/kernel/traps.c:175 [inline]
>  fixup_bug arch/x86/kernel/traps.c:170 [inline]
>  do_error_trap+0x12b/0x220 arch/x86/kernel/traps.c:267
>  do_invalid_op+0x32/0x40 arch/x86/kernel/traps.c:286
>  invalid_op+0x23/0x30 arch/x86/entry/entry_64.S:1027
> RIP: 0010:snd_pcm_plug_alloc+0x29a/0x330 sound/core/oss/pcm_plugin.c:126
> Code: ff ff 45 31 e4 e8 d6 4d 7f fb 44 89 e0 5b 5d 41 5c 41 5d 41 5e c3 e8 c5 4d 7f fb 0f 0b 41 bc fa ff ff ff eb e0 e8 b6 4d 7f fb <0f> 0b 41 bc fa ff ff ff eb d1 e8 a7 4d 7f fb 0f 0b 41 bc fa ff ff
> RSP: 0018:ffffc90002317b88 EFLAGS: 00010293
> RAX: ffff888093a7c200 RBX: ffff8880a4086000 RCX: ffffffff85f37886
> RDX: 0000000000000000 RSI: ffffffff85f37a0a RDI: 0000000000000007
> RBP: 0000000000000000 R08: ffff888093a7c200 R09: ffffed10132a791f
> R10: ffff88809953c8f3 R11: ffffed10132a791e R12: ffff8880a4086058
> R13: dffffc0000000000 R14: 0000000000000000 R15: ffff88809953c800
>  snd_pcm_oss_change_params_locked+0x1c05/0x34b0 sound/core/oss/pcm_oss.c:1021
>  snd_pcm_oss_change_params+0x76/0xd0 sound/core/oss/pcm_oss.c:1084
>  snd_pcm_oss_make_ready+0xb7/0x170 sound/core/oss/pcm_oss.c:1143
>  snd_pcm_oss_sync.isra.0+0x1be/0x7d0 sound/core/oss/pcm_oss.c:1708
>  snd_pcm_oss_release+0x210/0x280 sound/core/oss/pcm_oss.c:2546
>  __fput+0x2da/0x850 fs/file_table.c:280
>  task_work_run+0xf4/0x1b0 kernel/task_work.c:123
>  tracehook_notify_resume include/linux/tracehook.h:188 [inline]
>  exit_to_usermode_loop+0x2fa/0x360 arch/x86/entry/common.c:165
>  prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
>  syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
>  do_syscall_64+0x6b1/0x7d0 arch/x86/entry/common.c:305
>  entry_SYSCALL_64_after_hwframe+0x49/0xbe
> RIP: 0033:0x4afb40
> Code: 8b 7c 24 10 48 8b 74 24 18 48 8b 54 24 20 49 c7 c2 00 00 00 00 49 c7 c0 00 00 00 00 49 c7 c1 00 00 00 00 48 8b 44 24 08 0f 05 <48> 3d 01 f0 ff ff 76 20 48 c7 44 24 28 ff ff ff ff 48 c7 44 24 30
> RSP: 002b:000000c000213588 EFLAGS: 00000212 ORIG_RAX: 0000000000000003
> RAX: 0000000000000000 RBX: 000000c00002c000 RCX: 00000000004afb40
> RDX: 0000000000000000 RSI: 0000000000000000 RDI: 0000000000000003
> RBP: 000000c0002135c8 R08: 0000000000000000 R09: 0000000000000000
> R10: 0000000000000000 R11: 0000000000000212 R12: 0000000000000006
> R13: 0000000000000005 R14: 0000000000000200 R15: 0000000000000000
> Kernel Offset: disabled
> Rebooting in 86400 seconds..
> 
> 
> ---
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