syzbot

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BUG: KCSAN: data-race in snd_ctl_notify / snd_ctl_notify

write to 0xffff8881269928b0 of 4 bytes by task 12387 on cpu 0:
 snd_ctl_notify sound/core/control.c:155 [inline]
 snd_ctl_notify+0xf4/0x3a0 sound/core/control.c:142
 loopback_active_notify+0xc1/0xd0 sound/drivers/aloop.c:373
 loopback_trigger+0x2b6/0x760 sound/drivers/aloop.c:427
 snd_pcm_do_start sound/core/pcm_native.c:1340 [inline]
 snd_pcm_do_start+0x65/0x80 sound/core/pcm_native.c:1335
 snd_pcm_action_single+0x56/0xc0 sound/core/pcm_native.c:1197
 snd_pcm_action+0x7d/0x90 sound/core/pcm_native.c:1280
 snd_pcm_start+0x28/0x40 sound/core/pcm_native.c:1381
 __snd_pcm_lib_xfer+0xc65/0x1078 sound/core/pcm_lib.c:2246
 snd_pcm_oss_write3+0xa7/0x190 sound/core/oss/pcm_oss.c:1221
 io_playback_transfer+0x19f/0x1d0 sound/core/oss/io.c:47
 snd_pcm_plug_write_transfer+0x219/0x290 sound/core/oss/pcm_plugin.c:622
 snd_pcm_oss_write2+0x178/0x270 sound/core/oss/pcm_oss.c:1353
 snd_pcm_oss_sync1+0xe9/0x270 sound/core/oss/pcm_oss.c:1594
 snd_pcm_oss_sync.isra.0+0x42b/0x4e0 sound/core/oss/pcm_oss.c:1670
 snd_pcm_oss_release+0x160/0x170 sound/core/oss/pcm_oss.c:2546
 __fput+0x1e9/0x500 fs/file_table.c:280
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xba/0x120 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881269928b0 of 4 bytes by task 12354 on cpu 1:
 snd_ctl_notify sound/core/control.c:155 [inline]
 snd_ctl_notify+0xdf/0x3a0 sound/core/control.c:142
 loopback_active_notify+0xc1/0xd0 sound/drivers/aloop.c:373
 loopback_trigger+0x2b6/0x760 sound/drivers/aloop.c:427
 snd_pcm_do_start sound/core/pcm_native.c:1340 [inline]
 snd_pcm_do_start+0x65/0x80 sound/core/pcm_native.c:1335
 snd_pcm_action_single+0x56/0xc0 sound/core/pcm_native.c:1197
 snd_pcm_action+0x7d/0x90 sound/core/pcm_native.c:1280
 snd_pcm_start+0x28/0x40 sound/core/pcm_native.c:1381
 __snd_pcm_lib_xfer+0xc65/0x1078 sound/core/pcm_lib.c:2246
 snd_pcm_oss_write3+0xa7/0x190 sound/core/oss/pcm_oss.c:1221
 io_playback_transfer+0x19f/0x1d0 sound/core/oss/io.c:47
 snd_pcm_plug_write_transfer+0x219/0x290 sound/core/oss/pcm_plugin.c:622
 snd_pcm_oss_write2+0x178/0x270 sound/core/oss/pcm_oss.c:1353
 snd_pcm_oss_sync1+0xe9/0x270 sound/core/oss/pcm_oss.c:1594
 snd_pcm_oss_sync.isra.0+0x42b/0x4e0 sound/core/oss/pcm_oss.c:1670
 snd_pcm_oss_release+0x160/0x170 sound/core/oss/pcm_oss.c:2546
 __fput+0x1e9/0x500 fs/file_table.c:280
 ____fput+0x1b/0x30 fs/file_table.c:313
 task_work_run+0xba/0x120 kernel/task_work.c:123
 tracehook_notify_resume include/linux/tracehook.h:188 [inline]
 exit_to_usermode_loop+0x2ae/0x2c0 arch/x86/entry/common.c:165
 prepare_exit_to_usermode arch/x86/entry/common.c:196 [inline]
 syscall_return_slowpath arch/x86/entry/common.c:279 [inline]
 do_syscall_64+0x38b/0x3b0 arch/x86/entry/common.c:305
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 12354 Comm: syz-executor.4 Not tainted 5.7.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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