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BUG: KCSAN: data-race in __ptrace_unlink / syscall_exit_work

write to 0xffff8880291ef028 of 4 bytes by task 27584 on cpu 0:
 __ptrace_unlink+0x160/0x2f0 kernel/ptrace.c:132
 __ptrace_detach+0x1b/0x1a0 kernel/ptrace.c:522
 exit_ptrace+0x93/0x160 kernel/ptrace.c:582
 forget_original_parent kernel/exit.c:613 [inline]
 exit_notify kernel/exit.c:653 [inline]
 do_exit+0x1219/0x1630 kernel/exit.c:829
 do_group_exit+0xc8/0x170 kernel/exit.c:906
 get_signal+0xf9b/0x1510 kernel/signal.c:2758
 arch_do_signal+0x25/0x260 arch/x86/kernel/signal.c:811
 exit_to_user_mode_loop kernel/entry/common.c:161 [inline]
 exit_to_user_mode_prepare+0xde/0x170 kernel/entry/common.c:191
 syscall_exit_to_user_mode+0x16/0x30 kernel/entry/common.c:266
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8880291ef028 of 4 bytes by task 27578 on cpu 1:
 ptrace_report_syscall include/linux/tracehook.h:60 [inline]
 tracehook_report_syscall_exit include/linux/tracehook.h:129 [inline]
 arch_syscall_exit_tracehook include/linux/entry-common.h:284 [inline]
 syscall_exit_work+0x7a/0x1b0 kernel/entry/common.c:231
 syscall_exit_to_user_mode_prepare+0x2f/0x40 kernel/entry/common.c:258
 syscall_exit_to_user_mode+0x9/0x30 kernel/entry/common.c:264
 do_syscall_64+0x45/0x80 arch/x86/entry/common.c:56
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27578 Comm: syz-executor.0 Not tainted 5.10.0-rc6-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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