KCSAN: data-race in do_group_exit / mm_release (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 09162bc3 Linux 5.10-rc4
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=167b4be6500000
kernel config: https://syzkaller.appspot.com/x/.config?x=e0bbcd06922dbd46
dashboard link: https://syzkaller.appspot.com/bug?extid=f06c9a522cdb9dcf9b77
compiler: clang version 12.0.0 (https://github.com/llvm/llvm-project.git 913f6005669cfb590c99865a90bc51ed0983d09d)
CC: [ak...@linux-foundation.org chri...@brauner.io ebie...@xmission.com linux-...@vger.kernel.org min...@kernel.org mi...@kernel.org pet...@infradead.org tg...@linutronix.de]

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+f06c9a...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_group_exit / mm_release

write to 0xffff8881026771b4 of 4 bytes by task 27288 on cpu 0:
do_group_exit+0x130/0x170 kernel/exit.c:900
__do_sys_exit_group+0xb/0x10 kernel/exit.c:917
__se_sys_exit_group+0x5/0x10 kernel/exit.c:915
__x64_sys_exit_group+0x16/0x20 kernel/exit.c:915
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

read to 0xffff8881026771b4 of 4 bytes by task 27305 on cpu 1:
mm_release+0x92/0x1c0 kernel/fork.c:1299
exit_mm_release+0x21/0x30 kernel/fork.c:1323
exit_mm+0x4b/0x370 kernel/exit.c:438
do_exit+0x3c2/0x15a0 kernel/exit.c:796
__do_sys_exit+0xb/0x10 kernel/exit.c:875
__se_sys_exit+0x5/0x10 kernel/exit.c:873
__x64_sys_exit+0x16/0x20 kernel/exit.c:873
do_syscall_64+0x39/0x80 arch/x86/entry/common.c:46
entry_SYSCALL_64_after_hwframe+0x44/0xa9

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 27305 Comm: syz-executor.2 Not tainted 5.10.0-rc4-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.