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BUG: KCSAN: data-race in __ptrace_unlink / get_signal

write to 0xffff8881242e2550 of 8 bytes by task 7599 on cpu 1:
 __ptrace_unlink+0x59/0x320 kernel/ptrace.c:126
 __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+0x11ce/0x14a0 kernel/exit.c:845
 do_group_exit+0xce/0x1a0 kernel/exit.c:922
 get_signal+0xf93/0x15d0 kernel/signal.c:2868
 arch_do_signal_or_restart+0x8c/0x280 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:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881242e2550 of 8 bytes by task 7592 on cpu 0:
 ptrace_signal kernel/signal.c:2597 [inline]
 get_signal+0xc6d/0x15d0 kernel/signal.c:2756
 arch_do_signal_or_restart+0x8c/0x280 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:207
 __syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
 syscall_exit_to_user_mode+0x20/0x40 kernel/entry/common.c:300
 do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
 entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0xffff88812aada000 -> 0xffff888102834040

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 7592 Comm: syz-executor.3 Not tainted 5.15.0-rc3-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
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