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

[syzbot]

Hello,

syzbot found the following issue on:

HEAD commit: ea1013c15392 Merge tag 'bpf-fixes' of git://git.kernel.org..
git tree: upstream
console output: https://syzkaller.appspot.com/x/log.txt?x=156a531a580000
kernel config: https://syzkaller.appspot.com/x/.config?x=b319ff1b6a2797ca
dashboard link: https://syzkaller.appspot.com/bug?extid=1018d2d7b2f19b8cd455
compiler: Debian clang version 20.1.8 (++20250708063551+0c9f909b7976-1~exp1~20250708183702.136), Debian LLD 20.1.8
CC: [b...@alien8.de dave....@linux.intel.com h...@zytor.com linux-...@vger.kernel.org mi...@redhat.com tg...@linutronix.de x...@kernel.org]

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

Downloadable assets:
disk image: https://storage.googleapis.com/syzbot-assets/e71363ad5fa5/disk-ea1013c1.raw.xz
vmlinux: https://storage.googleapis.com/syzbot-assets/7d02687e9370/vmlinux-ea1013c1.xz
kernel image: https://storage.googleapis.com/syzbot-assets/1289ed40062b/bzImage-ea1013c1.xz

IMPORTANT: if you fix the issue, please add the following tag to the commit:
Reported-by: syzbot+1018d2...@syzkaller.appspotmail.com

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

write to 0xffff888161dc845c of 4 bytes by task 28 on cpu 1:
trc_wait_for_one_reader+0x283/0x380 kernel/rcu/tasks.h:1756
check_all_holdout_tasks_trace+0xcb/0x4b0 kernel/rcu/tasks.h:1946
rcu_tasks_wait_gp+0x3fd/0x530 kernel/rcu/tasks.h:885
rcu_tasks_one_gp+0x7f6/0x8e0 kernel/rcu/tasks.h:622
rcu_tasks_kthread+0xf7/0x110 kernel/rcu/tasks.h:658
kthread+0x489/0x510 kernel/kthread.c:463
ret_from_fork+0x149/0x290 arch/x86/kernel/process.c:158
ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff888161dc8000 of 3264 bytes by task 19119 on cpu 0:
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+0x6e/0x950 kernel/fork.c:919
copy_process+0x37d/0x1ef0 kernel/fork.c:2052
create_io_thread+0x71/0xa0 kernel/fork.c:2599
create_io_worker+0xdf/0x360 io_uring/io-wq.c:911
io_wq_create_worker io_uring/io-wq.c:339 [inline]
io_wq_enqueue+0x2c1/0x3a0 io_uring/io-wq.c:1038
io_queue_iowq+0x208/0x2f0 io_uring/io_uring.c:491
io_req_task_submit+0x69/0xa0 io_uring/io_uring.c:1432
__io_run_local_work_loop io_uring/io_uring.c:1344 [inline]
__io_run_local_work+0x2ea/0x580 io_uring/io_uring.c:1378
io_run_local_work_locked+0x5a/0x70 io_uring/io_uring.c:1400
__do_sys_io_uring_enter io_uring/io_uring.c:3293 [inline]
__se_sys_io_uring_enter+0xd71/0x1a30 io_uring/io_uring.c:3219
__x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3219
x64_sys_call+0x27e4/0x3000 arch/x86/include/generated/asm/syscalls_64.h:427
do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
do_syscall_64+0xd8/0x2c0 arch/x86/entry/syscall_64.c:94
entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 60928 PID: 19119 Comm: syz.3.16886 Not tainted syzkaller #0 PREEMPT(voluntary)
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
==================================================================


---
This report is generated by a bot. It may contain errors.
See https://goo.gl/tpsmEJ for more information about syzbot.
syzbot engineers can be reached at syzk...@googlegroups.com.

syzbot will keep track of this issue. See:
https://goo.gl/tpsmEJ#status for how to communicate with syzbot.

If the report is already addressed, let syzbot know by replying with:
#syz fix: exact-commit-title

If you want to overwrite report's subsystems, reply with:
#syz set subsystems: new-subsystem
(See the list of subsystem names on the web dashboard)

If the report is a duplicate of another one, reply with:
#syz dup: exact-subject-of-another-report

If you want to undo deduplication, reply with:
#syz undup