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BUG: KCSAN: data-race in do_notify_parent_cldstop / do_signal_stop

write to 0xffff8881377f1a20 of 4 bytes by task 30013 on cpu 1:
 do_signal_stop+0x100/0x710 kernel/signal.c:2392
 get_signal+0xa16/0x1610 kernel/signal.c:2787
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881377f1a20 of 4 bytes by task 30012 on cpu 0:
 do_notify_parent_cldstop+0x1a3/0x280 kernel/signal.c:2110
 get_signal+0x428/0x1610 kernel/signal.c:2661
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:789
 handle_signal_work kernel/entry/common.c:147 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:171 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:208
 __syscall_exit_to_user_mode_work kernel/entry/common.c:290 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:301
 do_syscall_64+0x56/0x90 arch/x86/entry/common.c:57
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00000014

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 30012 Comm: syz-executor.1 Not tainted 5.13.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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