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BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff88813d55b0f0 of 4 bytes by task 8773 on cpu 1:
 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+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

read to 0xffff88813d55b0f0 of 4 bytes by task 8776 on cpu 0:
 prepare_signal+0x258/0x660 kernel/signal.c:933
 __send_signal_locked+0x2f/0x700 kernel/signal.c:1084
 send_signal_locked+0x28d/0x3a0 kernel/signal.c:1247
 do_send_sig_info+0x9f/0xf0 kernel/signal.c:1300
 do_send_specific+0xc4/0x100 kernel/signal.c:3949
 do_tkill kernel/signal.c:3975 [inline]
 __do_sys_tgkill kernel/signal.c:3994 [inline]
 __se_sys_tgkill kernel/signal.c:3988 [inline]
 __x64_sys_tgkill+0x115/0x150 kernel/signal.c:3988
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xcd/0x1d0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x63/0x6b

value changed: 0x00000000 -> 0x00010001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 8776 Comm: syz-executor.1 Tainted: G        W          6.8.0-rc5-syzkaller-00163-gffd2cb6b718e #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/25/2024
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