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BUG: KCSAN: data-race in check_kill_permission / get_signal

write to 0xffff88810a2ab02c of 4 bytes by task 21396 on cpu 1:
 get_signal+0xd12/0x14e0 kernel/signal.c:2757
 arch_do_signal_or_restart+0x2a/0x270 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+0x11a/0x1b0 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+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88810a2ab02c of 4 bytes by task 8397 on cpu 0:
 check_kill_permission+0x44/0x2d0 kernel/signal.c:838
 group_send_sig_info kernel/signal.c:1414 [inline]
 kill_pid_info+0x4e/0x100 kernel/signal.c:1452
 kill_proc_info kernel/signal.c:1469 [inline]
 kill_something_info kernel/signal.c:1566 [inline]
 __do_sys_kill kernel/signal.c:3687 [inline]
 __se_sys_kill+0xd3/0x450 kernel/signal.c:3681
 __x64_sys_kill+0x2d/0x40 kernel/signal.c:3681
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8397 Comm: syz-executor.2 Not tainted 5.12.0-rc4-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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