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BUG: KCSAN: data-race in do_notify_parent_cldstop / prepare_signal

write to 0xffff8881008cf6a0 of 4 bytes by task 6992 on cpu 0:
 prepare_signal+0x3fe/0x680 kernel/signal.c:971
 __send_signal+0x64/0x760 kernel/signal.c:1095
 send_signal+0x281/0x390 kernel/signal.c:1258
 do_send_sig_info kernel/signal.c:1307 [inline]
 do_send_specific+0x13d/0x1c0 kernel/signal.c:3919
 do_tkill kernel/signal.c:3945 [inline]
 __do_sys_tgkill kernel/signal.c:3964 [inline]
 __se_sys_tgkill kernel/signal.c:3958 [inline]
 __x64_sys_tgkill+0x108/0x140 kernel/signal.c:3958
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881008cf6a0 of 4 bytes by task 6993 on cpu 1:
 do_notify_parent_cldstop+0x1a1/0x290 kernel/signal.c:2140
 do_signal_stop+0x526/0x700 kernel/signal.c:2475
 get_signal+0xa19/0x15d0 kernel/signal.c:2820
 arch_do_signal_or_restart+0x8c/0x280 arch/x86/kernel/signal.c:865
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000016 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6993 Comm: syz-executor.5 Not tainted 5.15.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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