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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff8685fc48 of 4 bytes by task 11405 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:126
 free_pids+0x54/0xb0 kernel/pid.c:159
 release_task+0x9a9/0xb60 kernel/exit.c:296
 wait_task_zombie kernel/exit.c:1269 [inline]
 wait_consider_task+0x114a/0x1660 kernel/exit.c:1496
 do_wait_thread kernel/exit.c:1559 [inline]
 __do_wait+0xfa/0x510 kernel/exit.c:1677
 do_wait+0xb7/0x260 kernel/exit.c:1711
 kernel_wait4+0x16b/0x1e0 kernel/exit.c:1870
 __do_sys_wait4 kernel/exit.c:1898 [inline]
 __se_sys_wait4 kernel/exit.c:1894 [inline]
 __x64_sys_wait4+0x91/0x120 kernel/exit.c:1894
 x64_sys_call+0x2a66/0x2ff0 arch/x86/include/generated/asm/syscalls_64.h:62
 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 0xffffffff8685fc48 of 4 bytes by task 2 on cpu 1:
 copy_process+0x14a6/0x2000 kernel/fork.c:2346
 kernel_clone+0x16c/0x5c0 kernel/fork.c:2603
 kernel_thread+0xac/0xe0 kernel/fork.c:2665
 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: 1 UID: 0 PID: 2 Comm: kthreadd Not tainted 6.16.0-syzkaller-11105-ga6923c06a3b2 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/12/2025
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