syzbot

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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff8881139e2b68 of 4 bytes by task 15332 on cpu 0:
 free_pid+0x77/0x180 kernel/pid.c:125
 free_pids+0x7a/0xb0 kernel/pid.c:158
 release_task+0x9d0/0xbb0 kernel/exit.c:289
 exit_notify kernel/exit.c:790 [inline]
 do_exit+0xee3/0x17c0 kernel/exit.c:973
 do_group_exit+0xff/0x140 kernel/exit.c:1102
 get_signal+0xe59/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x97/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x68/0xb0 kernel/entry/common.c:218
 do_syscall_64+0xdd/0x1a0 arch/x86/entry/syscall_64.c:100
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff8881139e2b68 of 4 bytes by task 11761 on cpu 1:
 zap_pid_ns_processes+0x1ff/0x2d0 kernel/pid_namespace.c:271
 find_child_reaper kernel/exit.c:630 [inline]
 forget_original_parent kernel/exit.c:719 [inline]
 exit_notify kernel/exit.c:756 [inline]
 do_exit+0x1525/0x17c0 kernel/exit.c:973
 do_group_exit+0xff/0x140 kernel/exit.c:1102
 get_signal+0xe59/0xf70 kernel/signal.c:3034
 arch_do_signal_or_restart+0x97/0x480 arch/x86/kernel/signal.c:337
 exit_to_user_mode_loop kernel/entry/common.c:111 [inline]
 exit_to_user_mode_prepare include/linux/entry-common.h:329 [inline]
 __syscall_exit_to_user_mode_work kernel/entry/common.c:207 [inline]
 syscall_exit_to_user_mode+0x68/0xb0 kernel/entry/common.c:218
 do_syscall_64+0xdd/0x1a0 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: 11761 Comm: syz-executor Not tainted 6.15.0-rc5-syzkaller-00123-g2c89c1b655c0 #0 PREEMPT(voluntary) 
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 04/19/2025
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