syzbot

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BUG: KCSAN: data-race in memcpy_and_pad / trc_wait_for_one_reader

write to 0xffff888156ec35dc of 4 bytes by task 28 on cpu 0:
 trc_wait_for_one_reader+0x282/0x380 kernel/rcu/tasks.h:1756
 check_all_holdout_tasks_trace+0xc3/0x480 kernel/rcu/tasks.h:1946
 rcu_tasks_wait_gp+0x408/0x540 kernel/rcu/tasks.h:885
 rcu_tasks_one_gp+0x7f1/0x8e0 kernel/rcu/tasks.h:622
 rcu_tasks_kthread+0xf6/0x110 kernel/rcu/tasks.h:658
 kthread+0x488/0x510 kernel/kthread.c:463
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

read to 0xffff888156ec3180 of 3264 bytes by task 18546 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+0x6e/0x940 kernel/fork.c:919
 copy_process+0x37e/0x1f10 kernel/fork.c:2052
 create_io_thread+0x8f/0xc0 kernel/fork.c:2599
 create_io_worker+0xde/0x360 io_uring/io-wq.c:911
 io_wq_create_worker io_uring/io-wq.c:339 [inline]
 io_wq_enqueue+0x461/0x540 io_uring/io-wq.c:1035
 io_queue_iowq+0x207/0x2f0 io_uring/io_uring.c:492
 io_req_task_submit+0x69/0xa0 io_uring/io_uring.c:1433
 __io_run_local_work_loop io_uring/io_uring.c:1345 [inline]
 __io_run_local_work+0x2eb/0x580 io_uring/io_uring.c:1379
 io_run_local_work_locked+0x5a/0x70 io_uring/io_uring.c:1401
 __do_sys_io_uring_enter io_uring/io_uring.c:3298 [inline]
 __se_sys_io_uring_enter+0x34c/0x1c70 io_uring/io_uring.c:3224
 __x64_sys_io_uring_enter+0x78/0x90 io_uring/io_uring.c:3224
 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+0xc0/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 60928 PID: 18546 Comm: syz.2.5243 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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