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BUG: KCSAN: data-race in snd_seq_oss_readq_poll / snd_seq_oss_readq_puts

write to 0xffff88811fb84508 of 4 bytes by task 14913 on cpu 1:
 snd_seq_oss_readq_put_event sound/core/seq/oss/seq_oss_readq.c:153 [inline]
 snd_seq_oss_readq_puts+0x150/0x1e0 sound/core/seq/oss/seq_oss_readq.c:100
 send_midi_event sound/core/seq/oss/seq_oss_midi.c:609 [inline]
 snd_seq_oss_midi_input+0x3ae/0x500 sound/core/seq/oss/seq_oss_midi.c:524
 snd_seq_oss_event_input+0xbc/0x100 sound/core/seq/oss/seq_oss_event.c:429
 snd_seq_deliver_single_event+0x31b/0x4f0 sound/core/seq/seq_clientmgr.c:638
 deliver_to_subscribers sound/core/seq/seq_clientmgr.c:693 [inline]
 snd_seq_deliver_event+0x392/0x4a0 sound/core/seq/seq_clientmgr.c:828
 snd_seq_kernel_client_dispatch+0x16f/0x190 sound/core/seq/seq_clientmgr.c:2323
 dummy_input+0xe3/0x110 sound/core/seq/seq_dummy.c:90
 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+0x20a/0x2d0 sound/core/seq/oss/seq_oss_midi.c:470
 snd_seq_oss_reset+0xbb/0x160 sound/core/seq/oss/seq_oss_init.c:440
 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+0x1df/0x460 fs/file_table.c:281
 ____fput+0x11/0x20 fs/file_table.c:314
 task_work_run+0x8e/0x110 kernel/task_work.c:123
 get_signal+0x14e2/0x1520 kernel/signal.c:2533
 do_signal+0x25/0x270 arch/x86/kernel/signal.c:810
 exit_to_usermode_loop arch/x86/entry/common.c:212 [inline]
 __prepare_exit_to_usermode+0x129/0x230 arch/x86/entry/common.c:246
 __syscall_return_slowpath arch/x86/entry/common.c:329 [inline]
 do_syscall_64+0xb9/0x120 arch/x86/entry/common.c:368
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811fb84508 of 4 bytes by task 14912 on cpu 0:
 snd_seq_oss_readq_poll+0x5d/0x70 sound/core/seq/oss/seq_oss_readq.c:209
 snd_seq_oss_poll+0x73/0x110 sound/core/seq/oss/seq_oss_rw.c:190
 odev_poll+0x3b/0x50 sound/core/seq/oss/seq_oss.c:194
 vfs_poll include/linux/poll.h:90 [inline]
 do_select+0x901/0xf40 fs/select.c:534
 core_sys_select+0x3e3/0x600 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+0x71/0x120 arch/x86/entry/common.c:359
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 14912 Comm: syz-executor.1 Not tainted 5.8.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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