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BUG: KCSAN: data-race in alloc_pid / copy_process

read-write to 0xffffffff8605c618 of 4 bytes by task 10 on cpu 0:
 alloc_pid+0x542/0x6f0 kernel/pid.c:284
 copy_process+0xff8/0x1f80 kernel/fork.c:2405
 kernel_clone+0x16a/0x570 kernel/fork.c:2796
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2874
 call_usermodehelper_exec_sync kernel/umh.c:133 [inline]
 call_usermodehelper_exec_work+0x7a/0x150 kernel/umh.c:164
 process_one_work kernel/workqueue.c:3254 [inline]
 process_scheduled_works+0x465/0x990 kernel/workqueue.c:3335
 worker_thread+0x526/0x730 kernel/workqueue.c:3416
 kthread+0x1d1/0x210 kernel/kthread.c:388
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

read to 0xffffffff8605c618 of 4 bytes by task 2 on cpu 1:
 copy_process+0x15d8/0x1f80 kernel/fork.c:2542
 kernel_clone+0x16a/0x570 kernel/fork.c:2796
 kernel_thread+0xb4/0xf0 kernel/fork.c:2858
 create_kthread kernel/kthread.c:411 [inline]
 kthreadd+0x28b/0x330 kernel/kthread.c:764
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x800000bf -> 0x800000c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 PID: 2 Comm: kthreadd Not tainted 6.9.0-rc4-syzkaller-00034-g4b6b51322118 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/27/2024
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