[moderation] [kernel?] KCSAN: data-race in task_participate_group_stop / wait_consider_task (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 79e8447ec662 Merge tag 'phy-fix-6.17' of git://git.kernel...
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=16b6f642580000
kernel config: https://syzkaller.appspot.com/x/.config?x=6e0c213d0735f5dd
dashboard link: https://syzkaller.appspot.com/bug?extid=abb06426bcf3a98e17cb
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [linux-...@vger.kernel.org lu...@kernel.org pet...@infradead.org tg...@linutronix.de]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/92c23cbdc6f9/disk-79e8447e.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/55f50d945fbb/vmlinux-79e8447e.xz
kernel image: https://storage.googleapis.com/syzbot-assets/fd1c8463e782/bzImage-79e8447e.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+abb064...@syzkaller.appspotmail.com

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

write to 0xffff888149cb44f4 of 4 bytes by task 21649 on cpu 0:
signal_set_stop_flags include/linux/sched/signal.h:275 [inline]
task_participate_group_stop+0x18f/0x1e0 kernel/signal.c:381
do_signal_stop+0x45c/0x5a0 kernel/signal.c:2617
get_signal+0x689/0xf70 kernel/signal.c:2985
arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
exit_to_user_mode_loop+0x7a/0x100 kernel/entry/common.c:40
exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888149cb44f4 of 4 bytes by task 21645 on cpu 1:
task_stopped_code kernel/exit.c:1289 [inline]
wait_task_stopped kernel/exit.c:1327 [inline]
wait_consider_task+0x381/0x1660 kernel/exit.c:1528
do_wait_thread kernel/exit.c:1554 [inline]
__do_wait+0xfa/0x510 kernel/exit.c:1672
do_wait+0xb7/0x260 kernel/exit.c:1706
kernel_waitid kernel/exit.c:1789 [inline]
__do_sys_waitid kernel/exit.c:1802 [inline]
__se_sys_waitid+0xca/0x2a0 kernel/exit.c:1797
__x64_sys_waitid+0x67/0x80 kernel/exit.c:1797
x64_sys_call+0xb0d/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:248
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000000 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 21645 Comm: Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
==================================================================


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