syzbot

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BUG: KCSAN: data-race in copy_process / memcpy_and_pad

write to 0xffff8881001d15f8 of 8 bytes by task 3865 on cpu 0:
 __list_add include/linux/list.h:153 [inline]
 list_add_tail include/linux/list.h:183 [inline]
 copy_process+0x1d42/0x1fe0 kernel/fork.c:2384
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2677
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffff8881001d1040 of 3200 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:98
 dup_task_struct+0x83/0x6a0 kernel/fork.c:873
 copy_process+0x399/0x1fe0 kernel/fork.c:1999
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 kernel_thread+0xac/0xe0 kernel/fork.c:2661
 create_kthread kernel/kthread.c:487 [inline]
 kthreadd+0x28d/0x360 kernel/kthread.c:847
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 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           6.16.0-rc1-syzkaller-00004-gaef17cb3d3c4 #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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