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BUG: KCSAN: data-race in snd_rawmidi_kernel_write1 / snd_rawmidi_write

write to 0xffff88809975e038 of 8 bytes by task 17419 on cpu 1:
 snd_rawmidi_kernel_write1+0x1e6/0x440 sound/core/rawmidi.c:1356
 snd_rawmidi_write+0x1c3/0x740 sound/core/rawmidi.c:1429
 __vfs_write+0x58/0xb0 fs/read_write.c:494
 __kernel_write+0xb0/0x230 fs/read_write.c:515
 write_pipe_buf+0xad/0xe0 fs/splice.c:809
 splice_from_pipe_feed fs/splice.c:512 [inline]
 __splice_from_pipe+0x298/0x4a0 fs/splice.c:636
 splice_from_pipe+0xc2/0x100 fs/splice.c:671
 default_file_splice_write+0x41/0x90 fs/splice.c:821
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809975e038 of 8 bytes by task 17431 on cpu 0:
 snd_rawmidi_write+0x311/0x740 sound/core/rawmidi.c:1452
 __vfs_write+0x58/0xb0 fs/read_write.c:494
 __kernel_write+0xb0/0x230 fs/read_write.c:515
 write_pipe_buf+0xad/0xe0 fs/splice.c:809
 splice_from_pipe_feed fs/splice.c:512 [inline]
 __splice_from_pipe+0x298/0x4a0 fs/splice.c:636
 splice_from_pipe+0xc2/0x100 fs/splice.c:671
 default_file_splice_write+0x41/0x90 fs/splice.c:821
 do_splice_from fs/splice.c:863 [inline]
 direct_splice_actor+0x97/0xb0 fs/splice.c:1037
 splice_direct_to_actor+0x22f/0x540 fs/splice.c:992
 do_splice_direct+0x152/0x1d0 fs/splice.c:1080
 do_sendfile+0x396/0x810 fs/read_write.c:1520
 __do_sys_sendfile64 fs/read_write.c:1581 [inline]
 __se_sys_sendfile64 fs/read_write.c:1567 [inline]
 __x64_sys_sendfile64+0x121/0x140 fs/read_write.c:1567
 do_syscall_64+0xc7/0x390 arch/x86/entry/common.c:294
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 17431 Comm: syz-executor.3 Not tainted 5.6.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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