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BUG: KCSAN: data-race in __ptrace_unlink / syscall_exit_work

write to 0xffff888122fb0070 of 4 bytes by task 10308 on cpu 1:
 __ptrace_unlink+0x162/0x320 kernel/ptrace.c:133
 __ptrace_detach+0x1b/0x1d0 kernel/ptrace.c:539
 exit_ptrace+0x93/0x160 kernel/ptrace.c:599
 forget_original_parent kernel/exit.c:628 [inline]
 exit_notify kernel/exit.c:668 [inline]
 do_exit+0x1244/0x1530 kernel/exit.c:845
 do_group_exit+0xce/0x1a0 kernel/exit.c:922
 get_signal+0xfa3/0x15e0 kernel/signal.c:2808
 arch_do_signal_or_restart+0x2a/0x220 arch/x86/kernel/signal.c:865
 handle_signal_work kernel/entry/common.c:148 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:172 [inline]
 exit_to_user_mode_prepare+0x109/0x190 kernel/entry/common.c:209
 __syscall_exit_to_user_mode_work kernel/entry/common.c:291 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff888122fb0070 of 4 bytes by task 10306 on cpu 0:
 ptrace_report_syscall include/linux/tracehook.h:60 [inline]
 tracehook_report_syscall_exit include/linux/tracehook.h:130 [inline]
 arch_syscall_exit_tracehook include/linux/entry-common.h:297 [inline]
 syscall_exit_work+0xa5/0x1d0 kernel/entry/common.c:257
 syscall_exit_to_user_mode_prepare kernel/entry/common.c:284 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x33/0x40 kernel/entry/common.c:302
 do_syscall_64+0x49/0x90 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00010001 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 10306 Comm: syz-executor.2 Not tainted 5.14.0-rc1-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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