[moderation] [kernel?] KCSAN: data-race in memcpy_and_pad / zap_other_threads (3)

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: 46b513250491 Merge tag 'v7.0-rc5-smb3-client-fix' of git:/..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=14c936da580000
kernel config: https://syzkaller.appspot.com/x/.config?x=3a78dd265deac3a9
dashboard link: https://syzkaller.appspot.com/bug?extid=297947fc7c36989ff0e5
compiler: Debian clang version 21.1.8 (++20251221033036+2078da43e25a-1~exp1~20251221153213.50), Debian LLD 21.1.8
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/8f19c67785a8/disk-46b51325.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/11dbb9704e20/vmlinux-46b51325.xz
kernel image: https://storage.googleapis.com/syzbot-assets/190d9812e855/bzImage-46b51325.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+297947...@syzkaller.appspotmail.com

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

read-write to 0xffff888150ff1618 of 8 bytes by task 21969 on cpu 0:
task_clear_jobctl_pending kernel/signal.c:339 [inline]
zap_other_threads+0x114/0x290 kernel/signal.c:1345
do_group_exit+0xe3/0x140 kernel/exit.c:1113
__do_sys_exit_group kernel/exit.c:1129 [inline]
__se_sys_exit_group kernel/exit.c:1127 [inline]
__x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1127
x64_sys_call+0x3008/0x3020 arch/x86/include/generated/asm/syscalls_64.h:232
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff888150ff10c0 of 3328 bytes by task 21970 on cpu 1:
memcpy_and_pad+0x48/0x80 lib/string_helpers.c:1008
arch_dup_task_struct+0x2c/0x40 arch/x86/kernel/process.c:108
dup_task_struct+0x6e/0x950 kernel/fork.c:920
copy_process+0x37e/0x20b0 kernel/fork.c:2050
create_io_thread+0x8f/0xc0 kernel/fork.c:2601
create_io_worker+0xde/0x360 io_uring/io-wq.c:917
io_wq_create_worker io_uring/io-wq.c:341 [inline]
io_wq_enqueue+0x461/0x540 io_uring/io-wq.c:1059
io_queue_iowq+0x24e/0x350 io_uring/io_uring.c:431
io_queue_sqe_fallback+0xe6/0x140 io_uring/io_uring.c:1661
io_submit_sqe io_uring/io_uring.c:1915 [inline]
io_submit_sqes+0xdd0/0x1230 io_uring/io_uring.c:2043
__do_sys_io_uring_enter io_uring/io_uring.c:2604 [inline]
__se_sys_io_uring_enter+0x1c9/0xf50 io_uring/io_uring.c:2539
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:2539
x64_sys_call+0x1e16/0x3020 arch/x86/include/generated/asm/syscalls_64.h:427
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0x12c/0x370 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: 21970 Comm: syz.1.6392 Tainted: G W syzkaller #0 PREEMPT(full)
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
==================================================================


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