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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86c61f68 of 4 bytes by task 15872 on cpu 0:
 free_pid+0xbc/0x1e0 kernel/pid.c:124
 free_pids+0x9e/0xb0 kernel/pid.c:157
 release_task+0x9a7/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:777 [inline]
 do_exit+0xda4/0x1600 kernel/exit.c:988
 do_group_exit+0xfe/0x140 kernel/exit.c:1118
 get_signal+0xe54/0xf60 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:64 [inline]
 exit_to_user_mode_loop+0x6a/0x6f0 kernel/entry/common.c:98
 __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 include/linux/entry-common.h:325 [inline]
 do_syscall_64+0x249/0x370 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c61f68 of 4 bytes by task 2 on cpu 1:
 copy_process+0x1895/0x20d0 kernel/fork.c:2396
 kernel_clone+0x16b/0x5d0 kernel/fork.c:2654
 kernel_thread+0xe5/0x120 kernel/fork.c:2715
 create_kthread kernel/kthread.c:459 [inline]
 kthreadd+0x25b/0x320 kernel/kthread.c:817
 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: 0x80000146 -> 0x80000145

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2 Comm: kthreadd Tainted: G        W           syzkaller #0 PREEMPT(full) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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