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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86a60018 of 4 bytes by task 18212 on cpu 0:
 free_pid+0xb9/0x1d0 kernel/pid.c:126
 free_pids+0x9e/0xb0 kernel/pid.c:159
 release_task+0x9a7/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:777 [inline]
 do_exit+0xd56/0x1590 kernel/exit.c:983
 do_group_exit+0xfe/0x140 kernel/exit.c:1112
 get_signal+0xe4f/0xf60 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x450 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:41 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:75
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:256 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:159 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:194 [inline]
 do_syscall_64+0x1d3/0x2a0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86a60018 of 4 bytes by task 2 on cpu 1:
 copy_process+0x16e4/0x1f10 kernel/fork.c:2394
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2651
 kernel_thread+0xe5/0x120 kernel/fork.c:2712
 create_kthread kernel/kthread.c:486 [inline]
 kthreadd+0x26b/0x330 kernel/kthread.c:844
 ret_from_fork+0x148/0x280 arch/x86/kernel/process.c:158
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:246

value changed: 0x80000120 -> 0x8000011f

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2 Comm: kthreadd Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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