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BUG: KCSAN: data-race in __snd_pcm_lib_xfer / snd_pcm_do_drain_init

write to 0xffff8881aecec000 of 4 bytes by task 25179 on cpu 1:
 snd_pcm_do_drain_init+0x28c/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+0x2c5/0xa00 sound/core/pcm_native.c:2029
 snd_pcm_kernel_ioctl+0x1ae/0xc20 sound/core/pcm_native.c:3333
 snd_pcm_oss_sync+0xaf/0x690 sound/core/oss/pcm_oss.c:1697
 snd_pcm_oss_ioctl+0x614/0x2900 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 0xffff8881aecec000 of 4 bytes by task 25169 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_write3+0x182/0x210 sound/core/oss/pcm_oss.c:1221
 io_playback_transfer+0x7a/0x2b0 sound/core/oss/io.c:47
 snd_pcm_plug_write_transfer+0x1d0/0x360 sound/core/oss/pcm_plugin.c:624
 snd_pcm_oss_write2+0xe0/0x250 sound/core/oss/pcm_oss.c:1353
 snd_pcm_oss_write1 sound/core/oss/pcm_oss.c:1419 [inline]
 snd_pcm_oss_write+0x322/0x880 sound/core/oss/pcm_oss.c:2765
 vfs_write+0x1d0/0x6b0 fs/read_write.c:584
 ksys_write+0xce/0x180 fs/read_write.c:639
 __do_sys_write fs/read_write.c:651 [inline]
 __se_sys_write fs/read_write.c:648 [inline]
 __x64_sys_write+0x3e/0x50 fs/read_write.c:648
 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: 25169 Comm: syz-executor.1 Not tainted 5.9.0-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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