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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86860860 of 4 bytes by task 3738 on cpu 1:
 free_pid+0x77/0x180 kernel/pid.c:126
 copy_process+0x188b/0x1fe0 kernel/fork.c:2437
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 __do_sys_clone kernel/fork.c:2742 [inline]
 __se_sys_clone kernel/fork.c:2726 [inline]
 __x64_sys_clone+0xe6/0x120 kernel/fork.c:2726
 x64_sys_call+0x2c59/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:57
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd2/0x200 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86860860 of 4 bytes by task 2 on cpu 0:
 copy_process+0x148f/0x1fe0 kernel/fork.c:2342
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2599
 kernel_thread+0xac/0xe0 kernel/fork.c:2661
 create_kthread kernel/kthread.c:487 [inline]
 kthreadd+0x28d/0x360 kernel/kthread.c:847
 ret_from_fork+0xdd/0x150 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x800000da -> 0x800000d9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2 Comm: kthreadd Not tainted 6.16.0-rc2-syzkaller-00318-g739a6c93cc75 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 05/07/2025
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