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BUG: KCSAN: data-race in copy_process / free_pid

read-write to 0xffff88810751a928 of 4 bytes by task 13728 on cpu 0:
 free_pid+0xb9/0x1d0 kernel/pid.c:126
 free_pids+0x9e/0xb0 kernel/pid.c:159
 release_task+0x9a7/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:777 [inline]
 do_exit+0xd56/0x1590 kernel/exit.c:983
 do_group_exit+0xfe/0x140 kernel/exit.c:1112
 get_signal+0xe4f/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 0xffff88810751a928 of 4 bytes by task 13731 on cpu 1:
 copy_process+0x1895/0x20c0 kernel/fork.c:2396
 kernel_clone+0x16b/0x5b0 kernel/fork.c:2654
 __do_sys_clone3 kernel/fork.c:2956 [inline]
 __se_sys_clone3+0x1f5/0x230 kernel/fork.c:2935
 __x64_sys_clone3+0x31/0x40 kernel/fork.c:2935
 x64_sys_call+0x580/0x3020 arch/x86/include/generated/asm/syscalls_64.h:436
 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

value changed: 0x80000004 -> 0x80000003

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 13731 Comm: syz.5.2471 Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 01/24/2026
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