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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff868609a0 of 4 bytes by task 12060 on cpu 1:
 free_pid+0x77/0x180 kernel/pid.c:126
 free_pids+0x7a/0xb0 kernel/pid.c:159
 release_task+0x9a9/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:796 [inline]
 do_exit+0xee3/0x16f0 kernel/exit.c:979
 call_usermodehelper_exec_async+0x247/0x250 kernel/umh.c:122
 ret_from_fork+0x4e/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

read to 0xffffffff868609a0 of 4 bytes by task 8694 on cpu 0:
 copy_process+0x148f/0x1fe0 kernel/fork.c:2602
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2859
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2937
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 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+0x486/0x510 kernel/kthread.c:464
 ret_from_fork+0x4e/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x800000fc -> 0x800000fb

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 8694 Comm: kworker/u8:21 Tainted: G        W           6.15.0-syzkaller-01958-g785cdec46e92 #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
Workqueue: events_unbound call_usermodehelper_exec_work
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