DoSing Xend, unable to destroy domain

DoSing Xend, unable to destroy domain

[Jacob Gorm Hansen]

hi,

just for fun my domain overwrote the shared_info_page with some repeated 
random value, whereafter the domain stopped responding (no surprise there).

I could still 'xm list' my running domains, but trying to 'xm destroy' 
the dead domain left xm hanging, and xend unresponsive. The only way to 
get xend running again was by booting the machine.

Calling xc_destroy() in libxc directly still left the domain hanging.

This is in the unstable tree.

Jacob


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RE: DoSing Xend, unable to destroy domain

[Ian Pratt]

> just for fun my domain overwrote the shared_info_page with 
> some repeated 
> random value, whereafter the domain stopped responding (no 
> surprise there).
> 
> I could still 'xm list' my running domains, but trying to 'xm 
> destroy' 
> the dead domain left xm hanging, and xend unresponsive. The 
> only way to 
> get xend running again was by booting the machine.

That shouldn't happen, but I'm not totally surprised. We know xend needs
to be a bit more defensive -- its one of the reasons for the planned
rewrite.
 
> Calling xc_destroy() in libxc directly still left the domain hanging.

I suspect this is due to xend not correctly closing down and freeing the
shared pages for the device channels. This will stop Xen from doing the
final cleanup of the domain, though most of the memory will have been
freed. Domains lingering in this state are ugly but fairly harmless.

Ian





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Re: DoSing Xend, unable to destroy domain

[Jacob Gorm Hansen]

Ian Pratt wrote:

>>I could still 'xm list' my running domains, but trying to 'xm 
>>destroy' 
>>the dead domain left xm hanging, and xend unresponsive. The 
>>only way to 
>>get xend running again was by booting the machine.
> 
> 
> That shouldn't happen, but I'm not totally surprised. We know xend needs
> to be a bit more defensive -- its one of the reasons for the planned
> rewrite.

Actually this a bit worse that I first thought, even a normal domU 
sitting in a tight loop seems immune to destruction :-(

Jacob


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