[alsa-devel] 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+52f83f0ea8df16932f7f at 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.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzkaller at googlegroups.com.

syzbot will keep track of this bug report. See:
https://goo.gl/tpsmEJ#bug-status-tracking for how to communicate with  
syzbot.
syzbot can test patches for this bug, for details see:
https://goo.gl/tpsmEJ#testing-patches