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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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