KCSAN: data-race in do_exit / exit_signals (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 67f34fa8 Merge tag 'usb-5.10-rc6' of git://git.kernel.org/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=17fe912d500000
kernel config: https://syzkaller.appspot.com/x/.config?x=9b9b19d1bde60f8d
dashboard link: https://syzkaller.appspot.com/bug?extid=74d5dfab4b8a37e04f6b
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ax...@kernel.dk chri...@brauner.io ebie...@xmission.com linux-...@vger.kernel.org liuzhi...@huawei.com 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+74d5df...@syzkaller.appspotmail.com

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

read-write to 0xffff88810e6a9024 of 4 bytes by task 6666 on cpu 0:
exit_signals+0x102/0x530 kernel/signal.c:2846
do_exit+0x15d/0x1630 kernel/exit.c:765
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 0xffff88810e6a9024 of 4 bytes by task 6675 on cpu 1:
find_alive_thread kernel/exit.c:496 [inline]
find_new_reaper kernel/exit.c:545 [inline]
forget_original_parent kernel/exit.c:620 [inline]
exit_notify kernel/exit.c:653 [inline]
do_exit+0x53c/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

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 6675 Comm: syz-executor.4 Not tainted 5.10.0-rc5-syzkaller #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/01/2011
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

[syzbot]

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