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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 80145ac2 Merge tag 's390-5.10-5' of git://git.kernel.org/p..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=1659d88b500000
kernel config: https://syzkaller.appspot.com/x/.config?x=cf114765a0c30afa
dashboard link: https://syzkaller.appspot.com/bug?extid=4622885d80fdbdcadcbf
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+462288...@syzkaller.appspotmail.com

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

read-write to 0xffff888028adb024 of 4 bytes by task 12454 on cpu 0:
freezer_count include/linux/freezer.h:121 [inline]
freezable_schedule include/linux/freezer.h:173 [inline]
ptrace_stop+0x36e/0x620 kernel/signal.c:2216
ptrace_signal kernel/signal.c:2491 [inline]
get_signal+0xbed/0x1510 kernel/signal.c:2654
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
irqentry_exit_to_user_mode+0x5/0x20 kernel/entry/common.c:279
irqentry_exit+0xe/0x40 kernel/entry/common.c:367
asm_exc_page_fault+0x1e/0x30 arch/x86/include/asm/idtentry.h:583

read to 0xffff888028adb024 of 4 bytes by task 12461 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: 12461 Comm: syz-executor.5 Not tainted 5.10.0-rc5-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.