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BUG: KCSAN: data-race in dequeue_signal / ptrace_check_attach

read-write to 0xffff888104636d20 of 8 bytes by task 8151 on cpu 1:
 dequeue_signal+0x2db/0x370 kernel/signal.c:656
 get_signal+0x356/0xf10 kernel/signal.c:2926
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x23c/0x3c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888104636d20 of 8 bytes by task 8150 on cpu 0:
 ptrace_freeze_traced kernel/ptrace.c:207 [inline]
 ptrace_check_attach+0xac/0x290 kernel/ptrace.c:274
 __do_sys_ptrace kernel/ptrace.c:1435 [inline]
 __se_sys_ptrace+0xd3/0x2c0 kernel/ptrace.c:1413
 __x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1413
 x64_sys_call+0x287b/0x3020 arch/x86/include/generated/asm/syscalls_64.h:102
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x136/0x3c0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x0000000000000000 -> 0x0000000008010000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 8150 Comm: syz.8.779 Tainted: G        W           syzkaller #0 PREEMPT(lazy) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/16/2026
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