[syzbot] [kernel?] KCSAN: data-race in do_notify_parent_cldstop / wait_consider_task (4)

[syzbot] [kernel?] KCSAN: data-race in do_notify_parent_cldstop / wait_consider_task (4)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit:    5e0f8396d480 Merge tag 'hid-for-linus-2026100201' of git:/..
git tree:       upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=12a48bf5580000
kernel config:  https://syzkaller.appspot.com/x/.config?x=ea1e6d8de13bab08
dashboard link: https://syzkaller.appspot.com/bug?extid=0f4d5234b6cb5e479e5d
compiler:       Debian clang version 22.1.8 (++20260613092233+e80beda6e255-1~exp1~20260613092250.77), Debian LLD 22.1.8

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/a60e785a1197/disk-5e0f8396.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/a44e17a91920/vmlinux-5e0f8396.xz
kernel image: https://storage.googleapis.com/syzbot-assets/3cc64997d7b1/bzImage-5e0f8396.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+0f4d5234b6cb5e479e5d@syzkaller.appspotmail.com

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

write to 0xffff8881049cca94 of 4 bytes by task 6287 on cpu 0:
 wait_task_stopped kernel/exit.c:1369 [inline]
 wait_consider_task+0x5db/0x15f0 kernel/exit.c:1555
 do_wait_pid kernel/exit.c:1657 [inline]
 __do_wait+0x33c/0x500 kernel/exit.c:1692
 do_wait+0xb6/0x230 kernel/exit.c:1733
 kernel_wait4+0x19f/0x210 kernel/exit.c:1892
 __do_sys_wait4 kernel/exit.c:1920 [inline]
 __se_sys_wait4 kernel/exit.c:1916 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1916
 x64_sys_call+0x108f/0x2550 arch/x86/include/generated/asm/syscalls_64.h:62
 do_syscall_x64 arch/x86/entry/syscall_64.c:61 [inline]
 do_syscall_64+0x112/0x360 arch/x86/entry/syscall_64.c:84
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881049cca94 of 4 bytes by task 6289 on cpu 1:
 do_notify_parent_cldstop+0x1fa/0x2f0 kernel/signal.c:2396
 ptrace_stop+0x2fa/0x590 kernel/signal.c:2514
 ptrace_signal+0x52/0x240 kernel/signal.c:2820
 get_signal+0x799/0xf10 kernel/signal.c:2999
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:343 [inline]
 do_syscall_64+0x212/0x360 arch/x86/entry/syscall_64.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000013 -> 0x00000000

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6289 Comm: syz.3.813 Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 09/16/2026
==================================================================


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