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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff8685f030 of 4 bytes by task 16992 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:125
 free_pids+0x54/0xb0 kernel/pid.c:158
 release_task+0x9d0/0xbb0 kernel/exit.c:289
 wait_task_zombie kernel/exit.c:1264 [inline]
 wait_consider_task+0x113f/0x1650 kernel/exit.c:1491
 do_wait_thread kernel/exit.c:1554 [inline]
 __do_wait+0xfa/0x510 kernel/exit.c:1672
 do_wait+0xb7/0x260 kernel/exit.c:1706
 kernel_wait4+0x16b/0x1e0 kernel/exit.c:1865
 __do_sys_wait4 kernel/exit.c:1893 [inline]
 __se_sys_wait4 kernel/exit.c:1889 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1889
 x64_sys_call+0x26c8/0x2fb0 arch/x86/include/generated/asm/syscalls_64.h:62
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd0/0x1a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8685f030 of 4 bytes by task 2 on cpu 1:
 copy_process+0x1790/0x1f90 kernel/fork.c:2587
 kernel_clone+0x16c/0x5b0 kernel/fork.c:2844
 kernel_thread+0xac/0xe0 kernel/fork.c:2906
 create_kthread kernel/kthread.c:487 [inline]
 kthreadd+0x28d/0x360 kernel/kthread.c:847
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:153
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:245

value changed: 0x800000fe -> 0x800000fd

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 2 Comm: kthreadd Not tainted 6.15.0-rc4-syzkaller-00011-gf15d97df5afa #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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