syzbot

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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86c5c3a8 of 4 bytes by task 3302 on cpu 0:
 free_pid+0xb3/0x1b0 kernel/pid.c:124
 free_pids+0x54/0xb0 kernel/pid.c:156
 release_task+0x9a7/0xb60 kernel/exit.c:295
 wait_task_zombie kernel/exit.c:1281 [inline]
 wait_consider_task+0x1160/0x1670 kernel/exit.c:1508
 do_wait_thread kernel/exit.c:1571 [inline]
 __do_wait+0xf9/0x510 kernel/exit.c:1689
 do_wait+0xb6/0x230 kernel/exit.c:1723
 kernel_wait4+0x19f/0x210 kernel/exit.c:1882
 __do_sys_wait4 kernel/exit.c:1910 [inline]
 __se_sys_wait4 kernel/exit.c:1906 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1906
 x64_sys_call+0x2aee/0x3020 arch/x86/include/generated/asm/syscalls_64.h:62
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x3b0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c5c3a8 of 4 bytes by task 40 on cpu 1:
 copy_process+0x1af1/0x2370 kernel/fork.c:2442
 kernel_clone+0x1a5/0x5e0 kernel/fork.c:2721
 user_mode_thread+0x9c/0xd0 kernel/fork.c:2797
 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:3314 [inline]
 process_scheduled_works+0x4f0/0x9c0 kernel/workqueue.c:3397
 worker_thread+0x58a/0x780 kernel/workqueue.c:3478
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x146/0x330 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x8000009a -> 0x80000099

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 40 Comm: kworker/u8:2 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/18/2026
Workqueue: events_unbound call_usermodehelper_exec_work
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