KCSAN: data-race in __ptrace_unlink / do_exit (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 521b619a Merge tag 'linux-kselftest-kunit-fixes-5.10-rc3' ..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=120b4d8a500000
kernel config: https://syzkaller.appspot.com/x/.config?x=76dfc991796328d4
dashboard link: https://syzkaller.appspot.com/bug?extid=48549b693a904f20c247
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [linux-...@vger.kernel.org ol...@redhat.com]

Unfortunately, I don't have any reproducer for this issue yet.

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+48549b...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in __ptrace_unlink / do_exit

write to 0xffff888063c60028 of 4 bytes by task 22119 on cpu 0:
__ptrace_unlink+0x160/0x2f0 kernel/ptrace.c:132
__ptrace_detach+0x1b/0x1a0 kernel/ptrace.c:528
exit_ptrace+0x93/0x160 kernel/ptrace.c:588
forget_original_parent kernel/exit.c:610 [inline]
exit_notify kernel/exit.c:650 [inline]
do_exit+0x11b3/0x15a0 kernel/exit.c:826
do_group_exit+0xc8/0x170 kernel/exit.c:903
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 0xffff888063c60028 of 4 bytes by task 22117 on cpu 1:
ptrace_event_enabled include/linux/ptrace.h:142 [inline]
ptrace_event include/linux/ptrace.h:157 [inline]
do_exit+0xff/0x15a0 kernel/exit.c:747
do_group_exit+0xc8/0x170 kernel/exit.c:903
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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 22117 Comm: syz-executor.4 Not tainted 5.10.0-rc2-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


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[syzbot]

Auto-closing this bug as obsolete.
Crashes did not happen for a while, no reproducer and no activity.