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BUG: KCSAN: data-race in copy_process / memcpy_and_pad

write to 0xffff8881001d9638 of 8 bytes by task 32405 on cpu 0:
 __list_add include/linux/list.h:161 [inline]
 list_add_tail include/linux/list.h:191 [inline]
 copy_process+0x1c64/0x1f10 kernel/fork.c:2436
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 user_mode_thread+0x9c/0xd0 kernel/fork.c:2727
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3257 [inline]
 process_scheduled_works+0x4cd/0x9d0 kernel/workqueue.c:3340
 worker_thread+0x581/0x770 kernel/workqueue.c:3421
 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 0xffff8881001d9080 of 3264 bytes by task 2 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
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 kernel_thread+0xe5/0x120 kernel/fork.c:2712
 create_kthread kernel/kthread.c:486 [inline]
 kthreadd+0x26b/0x330 kernel/kthread.c:844
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2 Comm: kthreadd 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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