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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86860860 of 4 bytes by task 17685 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:126
 free_pids+0x7a/0xb0 kernel/pid.c:159
 release_task+0x9a9/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:782 [inline]
 do_exit+0xd81/0x1590 kernel/exit.c:976
 call_usermodehelper_exec_async+0x247/0x250 kernel/umh.c:122
 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 0xffffffff86860860 of 4 bytes by task 37 on cpu 1:
 copy_process+0x148f/0x1fe0 kernel/fork.c:2342
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2677
 call_usermodehelper_exec_work+0x41/0x160 kernel/umh.c:171
 process_one_work kernel/workqueue.c:3238 [inline]
 process_scheduled_works+0x4cb/0x9d0 kernel/workqueue.c:3321
 worker_thread+0x582/0x770 kernel/workqueue.c:3402
 kthread+0x489/0x510 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: 0x8000011a -> 0x80000119

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 37 Comm: kworker/u8:2 Tainted: G        W           6.16.0-rc4-syzkaller-00049-gb4911fb0b060 #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
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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bridge0: port 1(bridge_slave_0) entered blocking state
bridge0: port 1(bridge_slave_0) entered forwarding state