syzbot

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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86c5ffa8 of 4 bytes by task 10161 on cpu 0:
 free_pid+0xbc/0x1e0 kernel/pid.c:124
 free_pids+0x54/0xb0 kernel/pid.c:157
 release_task+0x9a7/0xb60 kernel/exit.c:295
 wait_task_zombie kernel/exit.c:1280 [inline]
 wait_consider_task+0x1160/0x1670 kernel/exit.c:1507
 do_wait_thread kernel/exit.c:1570 [inline]
 __do_wait+0xf9/0x510 kernel/exit.c:1688
 do_wait+0xb6/0x260 kernel/exit.c:1722
 kernel_wait4+0x19f/0x210 kernel/exit.c:1881
 __do_sys_wait4 kernel/exit.c:1909 [inline]
 __se_sys_wait4 kernel/exit.c:1905 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1905
 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/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c5ffa8 of 4 bytes by task 6125 on cpu 1:
 copy_process+0x187f/0x20b0 kernel/fork.c:2396
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2653
 user_mode_thread+0x9c/0xd0 kernel/fork.c:2729
 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:3276 [inline]
 process_scheduled_works+0x513/0xa10 kernel/workqueue.c:3359
 worker_thread+0x58a/0x780 kernel/workqueue.c:3440
 kthread+0x22a/0x280 kernel/kthread.c:436
 ret_from_fork+0x150/0x360 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x80000150 -> 0x8000014f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 6125 Comm: kworker/u8:33 Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
Workqueue: events_unbound call_usermodehelper_exec_work
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smc: removing ib device !yz2