KCSAN: data-race in do_notify_parent_cldstop / wait_consider_task

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: cf1d2c3e7e2f Merge tag 'nfsd-5.15-2' of git://git.kernel.o..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14da8017300000
kernel config: https://syzkaller.appspot.com/x/.config?x=11d01ee331121c57
dashboard link: https://syzkaller.appspot.com/bug?extid=dee8aba1873dd5de86bb
compiler: Debian clang version 11.0.1-2, GNU ld (GNU Binutils for Debian) 2.35.1
CC: [ak...@linux-foundation.org ax...@kernel.dk chri...@brauner.io ebie...@xmission.com jnew...@torproject.org linux-...@vger.kernel.org mathieu....@efficios.com min...@kernel.org ol...@redhat.com pet...@infradead.org]

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+dee8ab...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in do_notify_parent_cldstop / wait_consider_task

write to 0xffff8881279c84d0 of 4 bytes by task 5187 on cpu 1:
wait_task_stopped kernel/exit.c:1185 [inline]
wait_consider_task+0xbaf/0x1a10 kernel/exit.c:1371
ptrace_do_wait kernel/exit.c:1411 [inline]
do_wait+0x1f4/0x640 kernel/exit.c:1518
kernel_wait4+0x14b/0x1b0 kernel/exit.c:1677
__do_sys_wait4 kernel/exit.c:1705 [inline]
__se_sys_wait4 kernel/exit.c:1701 [inline]
__x64_sys_wait4+0x90/0x120 kernel/exit.c:1701
do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x44/0xa0 arch/x86/entry/common.c:80
entry_SYSCALL_64_after_hwframe+0x44/0xae

read to 0xffff8881279c84d0 of 4 bytes by task 5185 on cpu 0:
do_notify_parent_cldstop+0x1b7/0x290 kernel/signal.c:2143
ptrace_stop+0x2e2/0x670 kernel/signal.c:2287
ptrace_do_notify kernel/signal.c:2354 [inline]
ptrace_notify+0x107/0x180 kernel/signal.c:2364
ptrace_report_syscall include/linux/tracehook.h:66 [inline]
tracehook_report_syscall_exit include/linux/tracehook.h:130 [inline]
arch_syscall_exit_tracehook include/linux/entry-common.h:297 [inline]
syscall_exit_work+0xdc/0x1d0 kernel/entry/common.c:257
syscall_exit_to_user_mode_prepare kernel/entry/common.c:284 [inline]
__syscall_exit_to_user_mode_work kernel/entry/common.c:289 [inline]
syscall_exit_to_user_mode+0x33/0x40 kernel/entry/common.c:302
do_syscall_64+0x50/0xa0 arch/x86/entry/common.c:86
entry_SYSCALL_64_after_hwframe+0x44/0xae

value changed: 0x00000005 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 PID: 5185 Comm: syz-executor.0 Not tainted 5.15.0-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.