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BUG: KCSAN: data-race in prepare_signal / ptrace_attach

write to 0xffff88812fa8a030 of 4 bytes by task 12750 on cpu 1:
 ptrace_attach+0x217/0x4c0 kernel/ptrace.c:424
 __do_sys_ptrace kernel/ptrace.c:1297 [inline]
 __se_sys_ptrace+0xc1/0x2d0 kernel/ptrace.c:1277
 __x64_sys_ptrace+0x51/0x60 kernel/ptrace.c:1277
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff88812fa8a030 of 4 bytes by task 12751 on cpu 0:
 prepare_signal+0x27b/0x670 kernel/signal.c:930
 __send_signal+0x64/0x790 kernel/signal.c:1082
 send_signal+0x28b/0x3a0 kernel/signal.c:1245
 do_send_sig_info+0x9b/0xe0 kernel/signal.c:1294
 group_send_sig_info kernel/signal.c:1441 [inline]
 kill_pid_info+0x7f/0x100 kernel/signal.c:1475
 kill_proc_info kernel/signal.c:1492 [inline]
 do_rt_sigqueueinfo kernel/signal.c:3977 [inline]
 __do_sys_rt_sigqueueinfo kernel/signal.c:3993 [inline]
 __se_sys_rt_sigqueueinfo+0xc8/0x110 kernel/signal.c:3986
 __x64_sys_rt_sigqueueinfo+0x3f/0x50 kernel/signal.c:3986
 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
 do_syscall_64+0x44/0xd0 arch/x86/entry/common.c:80
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000000 -> 0x00010001

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 12751 Comm: syz-executor.3 Not tainted 5.16.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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