WARNING in __snd_rawmidi_transmit_ack

[syzbot]

Hello,

syzbot found the following crash on:

HEAD commit: 37b5dca2898d Merge tag 'rtc-4.18-2' of git://git.kernel.or..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12204d62400000
kernel config: https://syzkaller.appspot.com/x/.config?x=25856fac4e580aa7
dashboard link: https://syzkaller.appspot.com/bug?extid=52f83f0ea8df16932f7f
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
userspace arch: i386
syzkaller repro:https://syzkaller.appspot.com/x/repro.syz?x=148ea9a4400000

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+52f83f...@syzkaller.appspotmail.com

random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: sshd: uninitialized urandom read (32 bytes read)
random: cc1: uninitialized urandom read (8 bytes read)
IPVS: ftp: loaded support on port[0] = 21
WARNING: CPU: 0 PID: 4608 at sound/core/rawmidi.c:1163
__snd_rawmidi_transmit_ack+0x263/0x2f0 sound/core/rawmidi.c:1163
Kernel panic - not syncing: panic_on_warn set ...

CPU: 0 PID: 4608 Comm: syz-executor0 Not tainted 4.18.0-rc4+ #51
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+0x1c9/0x2b4 lib/dump_stack.c:113
panic+0x238/0x4e7 kernel/panic.c:184
__warn.cold.8+0x163/0x1ba kernel/panic.c:536
report_bug+0x252/0x2d0 lib/bug.c:186
fixup_bug arch/x86/kernel/traps.c:178 [inline]
do_error_trap+0x1fc/0x4d0 arch/x86/kernel/traps.c:296
do_invalid_op+0x1b/0x20 arch/x86/kernel/traps.c:316
invalid_op+0x14/0x20 arch/x86/entry/entry_64.S:992
RIP: 0010:__snd_rawmidi_transmit_ack+0x263/0x2f0 sound/core/rawmidi.c:1163
Code: ba 01 00 00 00 be 03 00 00 00 e8 88 4a 83 fb e8 43 fe a2 fb 89 d8 48
83 c4 18 5b 41 5c 41 5d 41 5e 41 5f 5d c3 e8 2d fe a2 fb <0f> 0b e9 72 fe
ff ff e8 e1 dc e0 fb e9 1b ff ff ff bb ea ff ff ff
RSP: 0018:ffff8801abb8f720 EFLAGS: 00010093
RAX: ffff8801d8b500c0 RBX: 0000000000000002 RCX: ffffffff85d90b82
RDX: 0000000000000000 RSI: ffffffff85d90d13 RDI: 0000000000000006
RBP: ffff8801abb8f760 R08: ffff8801d8b500c0 R09: ffffed003b128cb4
R10: ffffed003b128cb4 R11: ffff8801d89465a3 R12: ffff8801cd646240
R13: 0000000000000802 R14: 0000000000000002 R15: ffff8801ab48e5c0
snd_virmidi_output_trigger+0x3ae/0x6b0 sound/core/seq/seq_virmidi.c:194
snd_rawmidi_output_trigger sound/core/rawmidi.c:150 [inline]
snd_rawmidi_kernel_write1+0x519/0x700 sound/core/rawmidi.c:1288
snd_rawmidi_write+0x2ea/0xde0 sound/core/rawmidi.c:1338
__vfs_write+0x117/0x9f0 fs/read_write.c:485
vfs_write+0x1f8/0x560 fs/read_write.c:549
ksys_write+0x101/0x260 fs/read_write.c:598
__do_sys_write fs/read_write.c:610 [inline]
__se_sys_write fs/read_write.c:607 [inline]
__ia32_sys_write+0x71/0xb0 fs/read_write.c:607
do_syscall_32_irqs_on arch/x86/entry/common.c:326 [inline]
do_fast_syscall_32+0x34d/0xfb2 arch/x86/entry/common.c:397
entry_SYSENTER_compat+0x70/0x7f arch/x86/entry/entry_64_compat.S:139
RIP: 0023:0xf7f5fcb9
Code: 55 08 8b 88 64 cd ff ff 8b 98 68 cd ff ff 89 c8 85 d2 74 02 89 0a 5b
5d c3 8b 04 24 c3 8b 1c 24 c3 51 52 55 89 e5 0f 34 cd 80 <5d> 5a 59 c3 90
90 90 90 eb 0d 90 90 90 90 90 90 90 90 90 90 90 90
RSP: 002b:00000000f7f190ac EFLAGS: 00000282 ORIG_RAX: 0000000000000004
RAX: ffffffffffffffda RBX: 0000000000000006 RCX: 00000000200000c0
RDX: 000000000000ff4c RSI: 0000000000000000 RDI: 0000000000000000
RBP: 0000000000000000 R08: 0000000000000000 R09: 0000000000000000
R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000
Dumping ftrace buffer:
(ftrace buffer empty)
Kernel Offset: disabled
Rebooting in 86400 seconds..


---
This bug is generated by a bot. It may contain errors.
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syzbot can test patches for this bug, for details see:
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[syzbot]

Hello,

syzbot tried to test the proposed patch but build/boot failed:

kernel clean failed: unsupported image type linux/386/gce


Tested on:

commit: 39675f7a7c7e ALSA: rawmidi: Change resized buffers atomica..
git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/topic/rawmidi-fixes

[Dmitry Vyukov]

On Tue, Jul 17, 2018 at 5:41 PM, syzbot
<syzbot+52f83f...@syzkaller.appspotmail.com> wrote:
> Hello,
>
> syzbot tried to test the proposed patch but build/boot failed:
>
> kernel clean failed: unsupported image type linux/386/gce

Looks like our problem. Looking into it.

> Tested on:
>
> commit: 39675f7a7c7e ALSA: rawmidi: Change resized buffers atomica..
> git tree:
> git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/topic/rawmidi-fixes
> compiler: gcc (GCC) 8.0.1 20180413 (experimental)
> userspace arch: i386
>

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[Dmitry Vyukov]

On Tue, Jul 17, 2018 at 5:48 PM, Dmitry Vyukov <dvy...@google.com> wrote:
> On Tue, Jul 17, 2018 at 5:41 PM, syzbot
> <syzbot+52f83f...@syzkaller.appspotmail.com> wrote:
>> Hello,
>>
>> syzbot tried to test the proposed patch but build/boot failed:
>>
>> kernel clean failed: unsupported image type linux/386/gce
>
> Looks like our problem. Looking into it.

Hopefully this is fixed now by
https://github.com/google/syzkaller/commit/6d5bd5b5eb9c988197c96ebfa3d17ecf5aea6311
so let's try again:

#syz test: git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git
topic/rawmidi-fixes

[syzbot]

Hello,

syzbot has tested the proposed patch and the reproducer did not trigger
crash:

Reported-and-tested-by:
syzbot+52f83f...@syzkaller.appspotmail.com

Tested on:

commit: 39675f7a7c7e ALSA: rawmidi: Change resized buffers atomica..
git tree:
git://git.kernel.org/pub/scm/linux/kernel/git/tiwai/sound.git/topic/rawmidi-fixes

kernel config: https://syzkaller.appspot.com/x/.config?x=8710ed53778d65e1

compiler: gcc (GCC) 8.0.1 20180413 (experimental)
userspace arch: i386

Note: testing is done by a robot and is best-effort only.