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BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff888129e820b0 of 4 bytes by task 13931 on cpu 0:
 ptrace_attach+0x31c/0x590 kernel/ptrace.c:459
 __do_sys_ptrace kernel/ptrace.c:1279 [inline]
 __se_sys_ptrace+0x149/0x2a0 kernel/ptrace.c:1261
 __x64_sys_ptrace+0x55/0x60 kernel/ptrace.c:1261
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0x59/0x120 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff888129e820b0 of 4 bytes by task 13932 on cpu 1:
 sig_ignored kernel/signal.c:118 [inline]
 prepare_signal+0x45a/0x660 kernel/signal.c:966
 __send_signal_locked+0x2f/0x700 kernel/signal.c:1084
 send_signal_locked+0x28d/0x3a0 kernel/signal.c:1247
 force_sig_info_to_task+0x1ec/0x280 kernel/signal.c:1351
 force_sig_fault_to_task kernel/signal.c:1726 [inline]
 force_sig_fault+0x73/0xa0 kernel/signal.c:1731
 __bad_area_nosemaphore+0x263/0x320 arch/x86/mm/fault.c:857
 handle_page_fault arch/x86/mm/fault.c:1505 [inline]
 exc_page_fault+0x500/0x6d0 arch/x86/mm/fault.c:1563
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:570

value changed: 0x00000000 -> 0x00010001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 13932 Comm: syz-executor.2 Not tainted 6.8.0-rc1-syzkaller-00385-g4854cf9c61d0 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 11/17/2023
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