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BUG: KCSAN: data-race in alloc_pid / copy_process

read-write to 0xffffffff8685f0b0 of 4 bytes by task 10936 on cpu 1:
 alloc_pid+0x539/0x720 kernel/pid.c:280
 copy_process+0xe0e/0x1f90 kernel/fork.c:2445
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2844
 __do_sys_clone3 kernel/fork.c:3148 [inline]
 __se_sys_clone3+0x1c2/0x200 kernel/fork.c:3127
 __x64_sys_clone3+0x31/0x40 kernel/fork.c:3127
 x64_sys_call+0x10c9/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:436
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8685f0b0 of 4 bytes by task 387 on cpu 0:
 copy_process+0x1790/0x1f90 kernel/fork.c:2587
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2844
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2922
 call_usermodehelper_exec_sync kernel/umh.c:132 [inline]
 call_usermodehelper_exec_work+0x7a/0x160 kernel/umh.c:163
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x489/0x510 kernel/kthread.c:464
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x800000bf -> 0x800000c0

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 387 Comm: kworker/u8:5 Not tainted 6.15.0-rc6-syzkaller-00051-g405e6c37c89e #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
Workqueue: events_unbound call_usermodehelper_exec_work
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