Jail causes host to reboot

Kozlov Sergey kozlov.sergey.404 at gmail.com
Wed Sep 2 19:32:31 UTC 2015


Anyways, any userspace program should not be able to crash the kernel,
so if you don't use self-modified OS and you're sure that everything is
ok with your hardware, you should really consider adding a bug to

Sergey Kozlov

On 02.09.2015 17:11, Adam Vande More wrote:
> On Wed, Sep 2, 2015 at 9:16 AM, Niklaas Baudet von Gersdorff <
> niklaas at kulturflatrate.net> wrote:
>> On 02/09/15 15:56, Adam Vande More wrote:
>> Thanks for this clarification.
>> So, in case someone is able to get access to a jail and causes a kernel
>> panic, the person can compromise the entire host system?
> Yes, depending on configuration.  It's trivial to make a jail insecure.
> The trick is to make a jail secure and fully functional for your needs.
>> I doubt that it is possible but you saying "depending on configuration"
>> brought up the following question: Is there a way to tell the host
>> system to only shut down the jail (and maybe send an email to me) in
>> case the jail causes a panic and not reboot the entire system?
> The host and jails use the same kernel, so if there's a panic it all goes
> down.  A separate monitoring and alerting platform is the only reliable way
> I know to get emails if something goes down.
> Am I right that the only way to prevent such failure is virtualising an
>> entire operating system instead of using a jail?
> Yes, but virtualizing is a loaded term.  Some people don't consider jails
> as virtualization.  I do, at least from a certain point of view.
> Especially now since independent FS's and network stacks can be involved.
> Then you have types like container eg OpenVZ(there was FreeBSD version of
> this floating around on 9.x, not sure what happened to it).  The guest in
> container's have independent kernels so the host would survive in my
> original scenario.  Same w/ other virtualization types like KVM, bhyve,
> VBox, Xen, etc.

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