syzbot

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BUG: KCSAN: data-race in snd_rawmidi_drain_output / snd_rawmidi_transmit

write to 0xffff88811f9fb1b8 of 8 bytes by task 3222 on cpu 1:
 __snd_rawmidi_transmit_ack sound/core/rawmidi.c:1255 [inline]
 snd_rawmidi_transmit+0x2e6/0x410 sound/core/rawmidi.c:1314
 snd_vmidi_output_work+0xf1/0x200 sound/core/seq/seq_virmidi.c:144
 process_one_work+0x3e1/0x9a0 kernel/workqueue.c:2269
 worker_thread+0x665/0xbe0 kernel/workqueue.c:2415
 kthread+0x20d/0x230 kernel/kthread.c:291
 ret_from_fork+0x1f/0x30 arch/x86/entry/entry_64.S:293

read to 0xffff88811f9fb1b8 of 8 bytes by task 11356 on cpu 0:
 snd_rawmidi_drain_output+0x31a/0x400 sound/core/rawmidi.c:222
 close_substream+0x14c/0x2e0 sound/core/rawmidi.c:510
 rawmidi_release_priv+0x96/0xf0 sound/core/rawmidi.c:536
 snd_rawmidi_release+0x33/0x80 sound/core/rawmidi.c:567
 __fput+0x1df/0x460 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:135
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop arch/x86/entry/common.c:239 [inline]
 __prepare_exit_to_usermode+0x1c6/0x230 arch/x86/entry/common.c:269
 __syscall_return_slowpath+0x47/0x60 arch/x86/entry/common.c:352
 do_syscall_64+0x5d/0xb0 arch/x86/entry/common.c:393
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 11356 Comm: syz-executor.4 Not tainted 5.8.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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