Re: [PATCH nf 0/1] netfilter: x_tables: avoid holding mutex over faultable user copies

[Pablo Neira Ayuso <pablo@netfilter.org>]

On Tue, Sep 01, 2026 at 01:47:53PM +0000, Zihan Xi wrote:
[...]
> Reproducer:
> 
> The following files must be saved with these exact names in one directory.
> The commands below build all helpers and run the FUSE/user-namespace path.
> The FUSE helper binary is named poc-userns-trig so the hung-task comm
> matches the crash log. The captured panic is hung_task after that task
> blocked for more than 10 seconds, and then khungtaskd panics because
> hung_task_panic=1. A 10-second timeout alone only warns; it does not
> panic. The tested guest enabled panic on the kernel command line with
> hung_task_panic=1 hung_task_timeout_secs=10
> hung_task_check_interval_secs=10 panic=-1. poc.sh, poc-userns-trig and
> poc.c also write these sysctls when they are writable:
> 
>     echo 10 > /proc/sys/kernel/hung_task_timeout_secs
>     echo 10 > /proc/sys/kernel/hung_task_check_interval_secs
>     echo 10 > /proc/sys/kernel/hung_task_warnings
>     echo 1 > /proc/sys/kernel/hung_task_panic

This configuration does not look sensible to me.