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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff88810cfe58e8 of 4 bytes by task 4023 on cpu 1:
 free_pid+0xb3/0x1b0 kernel/pid.c:124
 free_pids+0x54/0xb0 kernel/pid.c:156
 release_task+0x990/0xb40 kernel/exit.c:300
 exit_notify kernel/exit.c:810 [inline]
 do_exit+0xd79/0x1500 kernel/exit.c:1021
 do_group_exit+0xfe/0x140 kernel/exit.c:1152
 get_signal+0xe07/0xf10 kernel/signal.c:3046
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x23c/0x3c0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810cfe58e8 of 4 bytes by task 3304 on cpu 0:
 zap_pid_ns_processes+0x1fd/0x2d0 kernel/pid_namespace.c:272
 find_child_reaper kernel/exit.c:657 [inline]
 forget_original_parent kernel/exit.c:741 [inline]
 exit_notify kernel/exit.c:778 [inline]
 do_exit+0x13fa/0x1500 kernel/exit.c:1021
 do_group_exit+0xfe/0x140 kernel/exit.c:1152
 get_signal+0xe07/0xf10 kernel/signal.c:3046
 arch_do_signal_or_restart+0x96/0x480 arch/x86/kernel/signal.c:337
 __exit_to_user_mode_loop kernel/entry/common.c:66 [inline]
 exit_to_user_mode_loop+0x15d/0x8c0 kernel/entry/common.c:101
 __exit_to_user_mode_prepare include/linux/irq-entry-common.h:207 [inline]
 syscall_exit_to_user_mode_prepare include/linux/irq-entry-common.h:230 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:318 [inline]
 do_syscall_64+0x23c/0x3c0 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: 0 UID: 0 PID: 3304 Comm: syz-executor Not tainted syzkaller #0 PREEMPT(lazy) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 07/24/2026
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