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BUG: KCSAN: data-race in dequeue_signal / ptrace_check_attach

read-write to 0xffff8881087f9540 of 8 bytes by task 26728 on cpu 1:
 dequeue_signal+0x3ca/0x420 kernel/signal.c:694
 get_signal+0x366/0x1090 kernel/signal.c:2772
 arch_do_signal_or_restart+0x95/0x4b0 arch/x86/kernel/signal.c:309
 exit_to_user_mode_loop+0x6f/0xe0 kernel/entry/common.c:168
 exit_to_user_mode_prepare+0x6c/0xb0 kernel/entry/common.c:204
 __syscall_exit_to_user_mode_work kernel/entry/common.c:285 [inline]
 syscall_exit_to_user_mode+0x26/0x140 kernel/entry/common.c:296
 ret_from_fork_asm+0x11/0x20 arch/x86/entry/entry_64.S:304

read to 0xffff8881087f9540 of 8 bytes by task 26721 on cpu 0:
 ptrace_freeze_traced kernel/ptrace.c:200 [inline]
 ptrace_check_attach+0x7e/0x280 kernel/ptrace.c:267
 __do_sys_ptrace kernel/ptrace.c:1300 [inline]
 __se_sys_ptrace+0xd4/0x2a0 kernel/ptrace.c:1278
 __x64_sys_ptrace+0x55/0x60 kernel/ptrace.c:1278
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x63/0xcd

value changed: 0x0000000000000000 -> 0x0000000008010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 26721 Comm: syz-executor.2 Not tainted 6.6.0-rc5-syzkaller-00067-g8182d7a3f1b8 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/06/2023
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