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BUG: KCSAN: data-race in __snd_pcm_lib_xfer / snd_pcm_kernel_ioctl

write to 0xffff88811d667000 of 4 bytes by task 10585 on cpu 1:
 snd_pcm_post_start sound/core/pcm_native.c:1368 [inline]
 snd_pcm_action_single sound/core/pcm_native.c:1209 [inline]
 snd_pcm_action sound/core/pcm_native.c:1290 [inline]
 snd_pcm_action_lock_irq sound/core/pcm_native.c:1305 [inline]
 snd_pcm_start_lock_irq sound/core/pcm_native.c:1398 [inline]
 snd_pcm_kernel_ioctl+0x764/0xc20 sound/core/pcm_native.c:3331
 snd_pcm_oss_set_trigger+0x3e9/0x490 sound/core/oss/pcm_oss.c:2102
 snd_pcm_oss_poll+0x429/0x520 sound/core/oss/pcm_oss.c:2831
 vfs_poll include/linux/poll.h:90 [inline]
 do_pollfd fs/select.c:869 [inline]
 do_poll fs/select.c:917 [inline]
 do_sys_poll+0x606/0xbc0 fs/select.c:1011
 __do_sys_ppoll fs/select.c:1111 [inline]
 __se_sys_ppoll+0x169/0x1b0 fs/select.c:1091
 __x64_sys_ppoll+0x63/0x70 fs/select.c:1091
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88811d667000 of 4 bytes by task 10591 on cpu 0:
 pcm_sanity_check sound/core/pcm_lib.c:2067 [inline]
 __snd_pcm_lib_xfer+0xe2/0x10e0 sound/core/pcm_lib.c:2130
 snd_pcm_oss_read3+0x2a1/0x390 sound/core/oss/pcm_oss.c:1260
 snd_pcm_oss_read2 sound/core/oss/pcm_oss.c:1471 [inline]
 snd_pcm_oss_read1 sound/core/oss/pcm_oss.c:1518 [inline]
 snd_pcm_oss_read+0x6e9/0x8b0 sound/core/oss/pcm_oss.c:2742
 do_loop_readv_writev fs/read_write.c:734 [inline]
 do_iter_read+0x2df/0x4b0 fs/read_write.c:955
 vfs_readv fs/read_write.c:1073 [inline]
 do_readv+0x13d/0x290 fs/read_write.c:1110
 __do_sys_readv fs/read_write.c:1201 [inline]
 __se_sys_readv fs/read_write.c:1198 [inline]
 __x64_sys_readv+0x41/0x50 fs/read_write.c:1198
 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: 0 PID: 10591 Comm: syz-executor.3 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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