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BUG: KCSAN: data-race in check_kill_permission / futex_wait_queue_me

write to 0xffff888105eed02c of 4 bytes by task 8362 on cpu 1:
 freezer_do_not_count include/linux/freezer.h:109 [inline]
 freezable_schedule include/linux/freezer.h:171 [inline]
 futex_wait_queue_me+0x186/0x250 kernel/futex.c:2606
 futex_wait+0x145/0x400 kernel/futex.c:2708
 do_futex+0x1062/0x1cd0 kernel/futex.c:3734
 __do_sys_futex kernel/futex.c:3797 [inline]
 __se_sys_futex+0x2a8/0x390 kernel/futex.c:3763
 __x64_sys_futex+0x74/0x80 kernel/futex.c:3763
 do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888105eed02c of 4 bytes by task 8357 on cpu 0:
 check_kill_permission+0x44/0x2d0 kernel/signal.c:838
 do_send_specific+0x7f/0x100 kernel/signal.c:3817
 do_tkill kernel/signal.c:3849 [inline]
 __do_sys_tgkill kernel/signal.c:3868 [inline]
 __se_sys_tgkill kernel/signal.c:3862 [inline]
 __x64_sys_tgkill+0x108/0x140 kernel/signal.c:3862
 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: 8357 Comm: syz-fuzzer 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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