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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff888104ba1b28 of 4 bytes by task 5582 on cpu 0:
 free_pid+0xbc/0x1e0 kernel/pid.c:124
 free_pids+0x7a/0xb0 kernel/pid.c:157
 release_task+0x9a7/0xb60 kernel/exit.c:295
 exit_notify kernel/exit.c:777 [inline]
 do_exit+0xd5c/0x15a0 kernel/exit.c:983
 do_group_exit+0xfe/0x140 kernel/exit.c:1112
 get_signal+0xe54/0xf60 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 0xffff888104ba1b28 of 4 bytes by task 3318 on cpu 1:
 zap_pid_ns_processes+0x1fd/0x2d0 kernel/pid_namespace.c:272
 find_child_reaper kernel/exit.c:622 [inline]
 forget_original_parent kernel/exit.c:706 [inline]
 exit_notify kernel/exit.c:743 [inline]
 do_exit+0x13ea/0x15a0 kernel/exit.c:983
 do_group_exit+0xfe/0x140 kernel/exit.c:1112
 get_signal+0xe54/0xf60 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

value changed: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3318 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(full) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2026
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