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BUG: KCSAN: data-race in free_pid / zap_pid_ns_processes

read-write to 0xffff88811f562028 of 4 bytes by task 4555 on cpu 0:
 free_pid+0x83/0x180 kernel/pid.c:139
 __change_pid+0x19a/0x1c0 kernel/pid.c:367
 detach_pid+0x1c/0x30 kernel/pid.c:372
 __unhash_process kernel/exit.c:131 [inline]
 __exit_signal kernel/exit.c:200 [inline]
 release_task+0x6e7/0xc20 kernel/exit.c:257
 exit_notify kernel/exit.c:775 [inline]
 do_exit+0xf5d/0x17f0 kernel/exit.c:958
 do_group_exit+0x102/0x150 kernel/exit.c:1087
 get_signal+0xeb9/0x1000 kernel/signal.c:3036
 arch_do_signal_or_restart+0x95/0x4b0 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+0x62/0x120 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

read to 0xffff88811f562028 of 4 bytes by task 3624 on cpu 1:
 zap_pid_ns_processes+0x1f2/0x2c0 kernel/pid_namespace.c:271
 find_child_reaper kernel/exit.c:611 [inline]
 forget_original_parent kernel/exit.c:700 [inline]
 exit_notify kernel/exit.c:737 [inline]
 do_exit+0x155d/0x17f0 kernel/exit.c:958
 do_group_exit+0x102/0x150 kernel/exit.c:1087
 get_signal+0xeb9/0x1000 kernel/signal.c:3036
 arch_do_signal_or_restart+0x95/0x4b0 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+0x62/0x120 kernel/entry/common.c:218
 do_syscall_64+0xd6/0x1c0 arch/x86/entry/common.c:89
 entry_SYSCALL_64_after_hwframe+0x77/0x7f

value changed: 0x00000002 -> 0x00000001

Reported by Kernel Concurrency Sanitizer on:
CPU: 1 UID: 0 PID: 3624 Comm: syz-executor Not tainted 6.14.0-rc5-syzkaller-00218-g2a520073e74f #0
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 02/12/2025
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