==================================================================
BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff86c61f68 of 4 bytes by task 3602 on cpu 1:
 free_pid+0xbc/0x1e0 kernel/pid.c:124
 free_pids+0x54/0xb0 kernel/pid.c:157
 release_task+0x9a7/0xb60 kernel/exit.c:295
 wait_task_zombie kernel/exit.c:1274 [inline]
 wait_consider_task+0x1160/0x1670 kernel/exit.c:1501
 do_wait_thread kernel/exit.c:1564 [inline]
 __do_wait+0xf9/0x510 kernel/exit.c:1682
 do_wait+0xb6/0x260 kernel/exit.c:1716
 kernel_wait4+0x19f/0x210 kernel/exit.c:1875
 __do_sys_wait4 kernel/exit.c:1903 [inline]
 __se_sys_wait4 kernel/exit.c:1899 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1899
 x64_sys_call+0x2aee/0x3020 arch/x86/include/generated/asm/syscalls_64.h:62
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0x12c/0x370 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff86c61f68 of 4 bytes by task 2 on cpu 0:
 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:490 [inline]
 kthreadd+0x25b/0x320 kernel/kthread.c:848
 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: 0x800001aa -> 0x800001a9

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 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
==================================================================