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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff8685ff98 of 4 bytes by task 24630 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:127
 free_pids+0x9e/0xb0 kernel/pid.c:160
 release_task+0x9a9/0xb60 kernel/exit.c:296
 exit_notify kernel/exit.c:778 [inline]
 do_exit+0xd81/0x15c0 kernel/exit.c:978
 do_group_exit+0xff/0x140 kernel/exit.c:1107
 get_signal+0xe58/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8685ff98 of 4 bytes by task 22989 on cpu 1:
 copy_process+0x17fc/0x2000 kernel/fork.c:2354
 kernel_clone+0x16c/0x5c0 kernel/fork.c:2609
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2685
 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:3263 [inline]
 process_scheduled_works+0x4ce/0x9d0 kernel/workqueue.c:3346
 worker_thread+0x582/0x770 kernel/workqueue.c:3427
 kthread+0x489/0x510 kernel/kthread.c:463
 ret_from_fork+0x122/0x1b0 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x8000020a -> 0x80000209

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 22989 Comm: kworker/u8:12 Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
Workqueue: events_unbound call_usermodehelper_exec_work
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