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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff888104de1588 of 4 bytes by task 32509 on cpu 0:
 free_pid+0xb9/0x1d0 kernel/pid.c:126
 free_pids+0x7a/0xb0 kernel/pid.c:159
 release_task+0x9b1/0xb70 kernel/exit.c:297
 exit_notify kernel/exit.c:779 [inline]
 do_exit+0xd91/0x15d0 kernel/exit.c:985
 do_group_exit+0xff/0x140 kernel/exit.c:1114
 get_signal+0xe58/0xf70 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:41 [inline]
 exit_to_user_mode_loop kernel/entry/common.c:75 [inline]
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:226 [inline]
 irqentry_exit_to_user_mode_prepare include/linux/irq-entry-common.h:270 [inline]
 irqentry_exit_to_user_mode include/linux/irq-entry-common.h:339 [inline]
 irqentry_exit+0xfb/0x560 kernel/entry/common.c:196
 asm_exc_page_fault+0x26/0x30 arch/x86/include/asm/idtentry.h:618

read to 0xffff888104de1588 of 4 bytes by task 31610 on cpu 1:
 zap_pid_ns_processes+0x1fe/0x2d0 kernel/pid_namespace.c:272
 find_child_reaper kernel/exit.c:624 [inline]
 forget_original_parent kernel/exit.c:708 [inline]
 exit_notify kernel/exit.c:745 [inline]
 do_exit+0x1424/0x15d0 kernel/exit.c:985
 do_group_exit+0x139/0x140 kernel/exit.c:1114
 __do_sys_exit_group kernel/exit.c:1125 [inline]
 __se_sys_exit_group kernel/exit.c:1123 [inline]
 __x64_sys_exit_group+0x1f/0x20 kernel/exit.c:1123
 x64_sys_call+0x2fff/0x3000 arch/x86/include/generated/asm/syscalls_64.h:232
 do_syscall_x64 arch/x86/entry/syscall_64.c:63 [inline]
 do_syscall_64+0xd8/0x2a0 arch/x86/entry/syscall_64.c:94
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 31610 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/25/2025
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