syzbot

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BUG: KCSAN: data-race in snd_ctl_ioctl / snd_ctl_notify

write to 0xffff8880a20ed050 of 4 bytes by task 25922 on cpu 1:
 snd_ctl_subscribe_events sound/core/control.c:1574 [inline]
 snd_ctl_ioctl+0x2f0/0xda0 sound/core/control.c:1724
 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 0xffff8880a20ed050 of 4 bytes by task 25924 on cpu 0:
 snd_ctl_notify+0xd9/0x320 sound/core/control.c:158
 __snd_ctl_add_replace+0x3b0/0x490 sound/core/control.c:382
 snd_ctl_elem_add+0x65b/0x930 sound/core/control.c:1511
 snd_ctl_elem_add_user sound/core/control.c:1541 [inline]
 snd_ctl_ioctl+0x76a/0xda0 sound/core/control.c:1718
 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: 25924 Comm: syz-executor.1 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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