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BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff888150222130 of 4 bytes by task 23853 on cpu 0:
 ptrace_attach+0x321/0x590 kernel/ptrace.c:462
 __do_sys_ptrace kernel/ptrace.c:1276 [inline]
 __se_sys_ptrace+0x149/0x2b0 kernel/ptrace.c:1258
 __x64_sys_ptrace+0x55/0x70 kernel/ptrace.c:1258
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

read to 0xffff888150222130 of 4 bytes by task 23848 on cpu 1:
 prepare_signal+0x258/0x670 kernel/signal.c:934
 __send_signal_locked+0x2f/0x700 kernel/signal.c:1085
 send_signal_locked+0x28f/0x3a0 kernel/signal.c:1248
 do_send_sig_info+0x9f/0xf0 kernel/signal.c:1301
 group_send_sig_info kernel/signal.c:1453 [inline]
 kill_pid_info_type+0x85/0xd0 kernel/signal.c:1493
 kill_pid_info kernel/signal.c:1507 [inline]
 kill_proc_info kernel/signal.c:1514 [inline]
 do_rt_sigqueueinfo kernel/signal.c:4063 [inline]
 __do_sys_rt_sigqueueinfo kernel/signal.c:4079 [inline]
 __se_sys_rt_sigqueueinfo+0xcd/0x110 kernel/signal.c:4072
 __x64_sys_rt_sigqueueinfo+0x43/0x50 kernel/signal.c:4072
 do_syscall_64+0xd3/0x1d0
 entry_SYSCALL_64_after_hwframe+0x72/0x7a

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 23848 Comm: syz-executor.2 Tainted: G        W          6.9.0-rc3-syzkaller-00011-g20cb38a7af88 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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