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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffffffff8665ef48 of 4 bytes by task 3298 on cpu 1:
 free_pid+0x7c/0x170 kernel/pid.c:125
 free_pids+0x54/0xb0 kernel/pid.c:158
 release_task+0x97d/0xb70 kernel/exit.c:286
 wait_task_zombie kernel/exit.c:1265 [inline]
 wait_consider_task+0x116e/0x1680 kernel/exit.c:1492
 do_wait_thread kernel/exit.c:1555 [inline]
 __do_wait+0x100/0x500 kernel/exit.c:1673
 do_wait+0xaf/0x270 kernel/exit.c:1707
 kernel_wait4+0x164/0x1d0 kernel/exit.c:1866
 __do_sys_wait4 kernel/exit.c:1894 [inline]
 __se_sys_wait4 kernel/exit.c:1890 [inline]
 __x64_sys_wait4+0x94/0x120 kernel/exit.c:1890
 x64_sys_call+0x25f3/0x2e10 arch/x86/include/generated/asm/syscalls_64.h:62
 do_syscall_x64 arch/x86/entry/common.c:52 [inline]
 do_syscall_64+0xc9/0x1c0 arch/x86/entry/common.c:83
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffffffff8665ef48 of 4 bytes by task 2 on cpu 0:
 copy_process+0x1756/0x1f60 kernel/fork.c:2554
 kernel_clone+0x167/0x5e0 kernel/fork.c:2811
 kernel_thread+0xbc/0xf0 kernel/fork.c:2873
 create_kthread kernel/kthread.c:487 [inline]
 kthreadd+0x28b/0x330 kernel/kthread.c:847
 ret_from_fork+0x4b/0x60 arch/x86/kernel/process.c:148
 ret_from_fork_asm+0x1a/0x30 arch/x86/entry/entry_64.S:244

value changed: 0x800000ac -> 0x800000ab

Reported by Kernel Concurrency Sanitizer on:
CPU: 0 UID: 0 PID: 2 Comm: kthreadd Not tainted 6.14.0-syzkaller-00685-g3ba7dfb8da62 #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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