Re: [Xenomai-help] Buffer Overrun -> Kernel Explosion

[Jan Kiszka <jan.kiszka@domain.hid>]

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Brian L. wrote:
> I'm finally set up with netconsole to catch panics/crashes when they
> happen so now I can report more information on the one I alluded to a
> week or two ago in my "General Question.." thread.
> 
> What I did to cause it was write past the end of a buffer returned by
> rt_queue_alloc. I'm not entirely sure if this message came at the
> moment of the write (unlikely, IMHO) or later when more xnheap
> activity took place. The crash popped up in several different ways
> depending on what code paths I enabled/disabled.
> 
> What concerns me is that polluting an xnheap can bring the system to
> its knees so harshly. I can see why it could be *very* hard to police
> this sort of problem without destroying the performance of xnheap, so
> it wouldn't surprise me if this is "normal". Still, though, it's sad
> that user-space code can bring the system down after something as
> innocent as a fencepost error in a string copy routine...
> 
> Thoughts? I've pasted the console dump below.
> 

I remember that control structures and data are tightly knotted in
xnheaps, but I agree with you that this should not lead so easily to
such crashes for user space apps. Maybe some magic number check could
help to reduce the chance for now.

A cleaner long-term solution would be to decouple both regions.
Philippe, is this feasible (I'm not that deep in the internals of xnheap)?

Jan


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