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BUG: KCSAN: data-race in alloc_pid / copy_process

read-write to 0xffffffff8665d8f8 of 4 bytes by task 19621 on cpu 1:
 alloc_pid+0x542/0x6f0 kernel/pid.c:284
 copy_process+0xfdf/0x1f70 kernel/fork.c:2389
 kernel_clone+0x167/0x5e0 kernel/fork.c:2780
 __do_sys_clone3 kernel/fork.c:3084 [inline]
 __se_sys_clone3+0x1b5/0x1f0 kernel/fork.c:3063
 __x64_sys_clone3+0x31/0x40 kernel/fork.c:3063
 x64_sys_call+0x287d/0x2d60 arch/x86/include/generated/asm/syscalls_64.h:436
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8665d8f8 of 4 bytes by task 11189 on cpu 0:
 copy_process+0x15ca/0x1f70 kernel/fork.c:2526
 kernel_clone+0x167/0x5e0 kernel/fork.c:2780
 user_mode_thread+0x7d/0xb0 kernel/fork.c:2858
 call_usermodehelper_exec_work+0x41/0x150 kernel/umh.c:172
 process_one_work kernel/workqueue.c:3229 [inline]
 process_scheduled_works+0x483/0x9a0 kernel/workqueue.c:3310
 worker_thread+0x51d/0x6f0 kernel/workqueue.c:3391
 kthread+0x1d1/0x210 kernel/kthread.c:389
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:147
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x80000203 -> 0x80000204

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 11189 Comm: kworker/u8:32 Not tainted 6.11.0-syzkaller-07262-g839c4f596f89 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 08/06/2024
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