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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff8685f030 of 4 bytes by task 13775 on cpu 1:
 free_pid+0x77/0x180 kernel/pid.c:125
 free_pids+0x54/0xb0 kernel/pid.c:158
 release_task+0x9d0/0xbb0 kernel/exit.c:289
 wait_task_zombie kernel/exit.c:1264 [inline]
 wait_consider_task+0x113f/0x1650 kernel/exit.c:1491
 do_wait_thread kernel/exit.c:1554 [inline]
 __do_wait+0xfa/0x510 kernel/exit.c:1672
 do_wait+0xb7/0x260 kernel/exit.c:1706
 kernel_wait4+0x16b/0x1e0 kernel/exit.c:1865
 __do_sys_wait4 kernel/exit.c:1893 [inline]
 __se_sys_wait4 kernel/exit.c:1889 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1889
 x64_sys_call+0x26c8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:62
 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 0xffffffff8685f030 of 4 bytes by task 37 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+0x4cb/0x9d0 kernel/workqueue.c:3319
 worker_thread+0x582/0x770 kernel/workqueue.c:3400
 kthread+0x486/0x510 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: 0x800000c2 -> 0x800000c1

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 37 Comm: kworker/u8:2 Not tainted 6.15.0-rc4-syzkaller-00052-g4f79eaa2ceac #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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