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BUG: KCSAN: data-race in copy_process / memcpy_and_pad

write to 0xffff888100232758 of 8 bytes by task 27690 on cpu 0:
 __list_add include/linux/list.h:161 [inline]
 list_add_tail include/linux/list.h:191 [inline]
 copy_process+0x1e05/0x20b0 kernel/fork.c:2438
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2653
 user_mode_thread+0x9c/0xd0 kernel/fork.c:2729
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3276 [inline]
 process_scheduled_works+0x513/0xa10 kernel/workqueue.c:3359
 worker_thread+0x58a/0x780 kernel/workqueue.c:3440
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff888100232180 of 3328 bytes by task 2 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
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2653
 kernel_thread+0xe5/0x120 kernel/fork.c:2714
 create_kthread kernel/kthread.c:459 [inline]
 kthreadd+0x25b/0x320 kernel/kthread.c:817
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

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