syzbot

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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff88810482d700 of 4 bytes by task 8331 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:127
 free_pids+0x54/0xb0 kernel/pid.c:160
 release_task+0x9a9/0xb60 kernel/exit.c:296
 exit_notify kernel/exit.c:778 [inline]
 do_exit+0xd81/0x15c0 kernel/exit.c:978
 do_group_exit+0xff/0x140 kernel/exit.c:1107
 get_signal+0xe58/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88810482d700 of 4 bytes by task 6601 on cpu 1:
 zap_pid_ns_processes+0x1fe/0x2d0 kernel/pid_namespace.c:272
 find_child_reaper kernel/exit.c:623 [inline]
 forget_original_parent kernel/exit.c:707 [inline]
 exit_notify kernel/exit.c:744 [inline]
 do_exit+0x1414/0x15c0 kernel/exit.c:978
 do_group_exit+0xff/0x140 kernel/exit.c:1107
 get_signal+0xe58/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x96/0x440 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop+0x77/0x110 kernel/entry/common.c:40
 exit_to_user_mode_prepare include/linux/irq-entry-common.h:225 [inline]
 syscall_exit_to_user_mode_work include/linux/entry-common.h:175 [inline]
 syscall_exit_to_user_mode include/linux/entry-common.h:210 [inline]
 do_syscall_64+0x1d6/0x200 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: 6601 Comm: syz-executor Tainted: G        W           syzkaller #0 PREEMPT(voluntary) 
Tainted: [W]=WARN
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 10/02/2025
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