[moderation] [kernel?] KCSAN: data-race in memcpy_and_pad / zap_other_threads (2)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 2061f18ad76e Merge tag 'caps-pr-20251204' of git://git.ker..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=11c79ab4580000
kernel config: https://syzkaller.appspot.com/x/.config?x=fe265072cbd2f67a
dashboard link: https://syzkaller.appspot.com/bug?extid=f065e89891aa2f9fb8e3
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [linux-...@vger.kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/68ad9eabb708/disk-2061f18a.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/756a6923eb62/vmlinux-2061f18a.xz
kernel image: https://storage.googleapis.com/syzbot-assets/dbf0c80cc61c/bzImage-2061f18a.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+f065e8...@syzkaller.appspotmail.com

==================================================================
BUG: KCSAN: data-race in memcpy_and_pad / zap_other_threads

read-write to 0xffff88810c7dd7b8 of 8 bytes by task 4563 on cpu 0:
task_clear_jobctl_pending kernel/signal.c:339 [inline]
zap_other_threads+0x114/0x290 kernel/signal.c:1345
do_group_exit+0xe4/0x140 kernel/exit.c:1109
__do_sys_exit_group kernel/exit.c:1125 [inline]
__se_sys_exit_group kernel/exit.c:1123 [inline]
__x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1123
x64_sys_call+0x2fff/0x3000 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810c7dd280 of 3264 bytes by task 4564 on cpu 1:
memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1007
arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
dup_task_struct+0x83/0x690 kernel/fork.c:876
copy_process+0x37d/0x1ef0 kernel/fork.c:2009
create_io_thread+0x71/0xa0 kernel/fork.c:2556
io_sq_offload_create+0x644/0x840 io_uring/sqpoll.c:517
io_uring_create+0x2f2/0x4e0 io_uring/io_uring.c:3644
io_uring_setup io_uring/io_uring.c:3715 [inline]
__do_sys_io_uring_setup io_uring/io_uring.c:3749 [inline]
__se_sys_io_uring_setup+0x1be/0x1d0 io_uring/io_uring.c:3740
__x64_sys_io_uring_setup+0x31/0x40 io_uring/io_uring.c:3740
x64_sys_call+0x244c/0x3000 arch/x86/include/generated/asm/syscalls_64.h:426
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 4564 Comm: syz.0.295 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


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