KCSAN: data-race in snd_seq_oss_writeq_sync / snd_seq_oss_writeq_sync

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: fa02fcd9 Merge tag 'media/v5.10-2' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b479b3500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=f7714adf54e43294c796
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [alsa-...@alsa-project.org linux-...@vger.kernel.org pe...@perex.cz ti...@suse.com]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f7714a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in snd_seq_oss_writeq_sync / snd_seq_oss_writeq_sync

write to 0xffff88801caaf510 of 4 bytes by task 5980 on cpu 0:
snd_seq_oss_writeq_sync+0x300/0x340 sound/core/seq/oss/seq_oss_writeq.c:112
snd_seq_oss_ioctl+0x701/0xa70 sound/core/seq/oss/seq_oss_ioctl.c:86
odev_ioctl+0x58/0xc0 sound/core/seq/oss/seq_oss.c:180
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88801caaf510 of 4 bytes by task 5984 on cpu 1:
snd_seq_oss_writeq_sync+0x207/0x340 sound/core/seq/oss/seq_oss_writeq.c:109
snd_seq_oss_ioctl+0x701/0xa70 sound/core/seq/oss/seq_oss_ioctl.c:86
odev_ioctl+0x58/0xc0 sound/core/seq/oss/seq_oss.c:180
vfs_ioctl fs/ioctl.c:48 [inline]
__do_sys_ioctl fs/ioctl.c:753 [inline]
__se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
__x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 5984 Comm: syz-executor.4 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.