syzbot

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BUG: KCSAN: data-race in snd_rawmidi_poll / snd_rawmidi_receive

write to 0xffff8880b1e5c4b8 of 8 bytes by task 27933 on cpu 0:
 snd_rawmidi_receive+0x2c0/0x4b0 sound/core/rawmidi.c:1001
 snd_virmidi_dev_receive_event sound/core/seq/seq_virmidi.c:88 [inline]
 snd_virmidi_event_input+0x1b1/0x250 sound/core/seq/seq_virmidi.c:110
 snd_seq_deliver_single_event+0x31b/0x4f0 sound/core/seq/seq_clientmgr.c:638
 snd_seq_deliver_event+0x192/0x4a0 sound/core/seq/seq_clientmgr.c:839
 snd_seq_kernel_client_dispatch+0x16f/0x190 sound/core/seq/seq_clientmgr.c:2323
 snd_seq_oss_dispatch sound/core/seq/oss/seq_oss_device.h:138 [inline]
 snd_seq_oss_midi_reset+0x24b/0x2d0 sound/core/seq/oss/seq_oss_midi.c:474
 snd_seq_oss_synth_reset+0x281/0x4a0 sound/core/seq/oss/seq_oss_synth.c:404
 snd_seq_oss_reset+0x3b/0x160 sound/core/seq/oss/seq_oss_init.c:435
 snd_seq_oss_release+0x76/0x170 sound/core/seq/oss/seq_oss_init.c:412
 odev_release+0x3a/0x60 sound/core/seq/oss/seq_oss.c:140
 __fput+0x246/0x4d0 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:141
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:163 [inline]
 exit_to_user_mode_prepare+0x1b2/0x210 kernel/entry/common.c:190
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:265
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880b1e5c4b8 of 8 bytes by task 27902 on cpu 1:
 snd_rawmidi_ready sound/core/rawmidi.c:102 [inline]
 snd_rawmidi_poll+0x170/0x210 sound/core/rawmidi.c:1502
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x8f6/0xf70 fs/select.c:534
 core_sys_select+0x3e3/0x610 fs/select.c:677
 do_pselect fs/select.c:759 [inline]
 __do_sys_pselect6 fs/select.c:800 [inline]
 __se_sys_pselect6+0x248/0x290 fs/select.c:791
 __x64_sys_pselect6+0x74/0x80 fs/select.c:791
 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: 27902 Comm: syz-executor.0 Not tainted 5.9.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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