syzbot

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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86860980 of 4 bytes by task 37 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
 wait_task_zombie kernel/exit.c:1270 [inline]
 wait_consider_task+0x113f/0x1650 kernel/exit.c:1497
 do_wait_pid kernel/exit.c:1636 [inline]
 __do_wait+0x34a/0x510 kernel/exit.c:1671
 do_wait+0xb7/0x260 kernel/exit.c:1712
 kernel_wait+0x51/0xc0 kernel/exit.c:1888
 call_usermodehelper_exec_sync kernel/umh.c:136 [inline]
 call_usermodehelper_exec_work+0x9c/0x160 kernel/umh.c:163
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4ce/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 0xffffffff86860980 of 4 bytes by task 31 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_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: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

value changed: 0x80000092 -> 0x80000091

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 31 Comm: kworker/u8:1 Not tainted 6.15.0-syzkaller-07774-g90b83efa6701 #0 PREEMPT(voluntary) 
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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