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BUG: KCSAN: data-race in alloc_pid / copy_process

read-write to 0xffffffff8685fc48 of 4 bytes by task 51 on cpu 0:
 alloc_pid+0x539/0x720 kernel/pid.c:281
 copy_process+0xe25/0x2000 kernel/fork.c:2191
 kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2683
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 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 0xffffffff8685fc48 of 4 bytes by task 31 on cpu 1:
 copy_process+0x14a6/0x2000 kernel/fork.c:2348
 kernel_clone+0x16c/0x5c0 kernel/fork.c:2605
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2683
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3236 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 kernel/kthread.c:463
 ret_from_fork+0xda/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x800000ff -> 0x80000100

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 31 Comm: kworker/u8:1 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
Workqueue: events_unbound call_usermodehelper_exec_work
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