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BUG: KCSAN: data-race in snd_pcm_do_drain_init / snd_pcm_drain

write to 0xffff88809a57e000 of 4 bytes by task 1899 on cpu 1:
 snd_pcm_do_drain_init+0x289/0x5b0 sound/core/pcm_native.c:1953
 snd_pcm_action_single sound/core/pcm_native.c:1207 [inline]
 snd_pcm_action sound/core/pcm_native.c:1290 [inline]
 snd_pcm_drain+0x901/0xa20 sound/core/pcm_native.c:2029
 snd_pcm_kernel_ioctl+0x1ae/0xc20 sound/core/pcm_native.c:3333
 snd_pcm_oss_sync+0xb2/0x680 sound/core/oss/pcm_oss.c:1697
 snd_pcm_oss_ioctl+0x613/0x2970 sound/core/oss/pcm_oss.c:2590
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff88809a57e000 of 4 bytes by task 1897 on cpu 0:
 snd_pcm_drain+0x82/0xa20 sound/core/pcm_native.c:2014
 snd_pcm_kernel_ioctl+0x1ae/0xc20 sound/core/pcm_native.c:3333
 snd_pcm_oss_sync+0xb2/0x680 sound/core/oss/pcm_oss.c:1697
 snd_pcm_oss_ioctl+0x613/0x2970 sound/core/oss/pcm_oss.c:2590
 vfs_ioctl fs/ioctl.c:48 [inline]
 __do_sys_ioctl fs/ioctl.c:753 [inline]
 __se_sys_ioctl+0xcb/0x140 fs/ioctl.c:739
 __x64_sys_ioctl+0x3f/0x50 fs/ioctl.c:739
 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: 1897 Comm: syz-executor.0 Not tainted 5.9.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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