Re: Follow up to NSE issues and gh_list assert() failure (Was 4.85BETA2 posted...)

[Brandon Enright <bmenrigh () ucsd edu>]

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On Wed, 25 Feb 2009 21:12:10 -0700 or thereabouts Patrick Donnelly
<batrick.donnelly () gmail com> wrote:

> On Wed, Feb 25, 2009 at 6:28 PM, Brandon Enright <bmenrigh () ucsd edu>
> wrote:
> > ==12614==
> > ==12614== Invalid read of size 8
> > ==12614==    at 0x58427C3: lua_pushboolean
...snip...
> I'm fairly certain this is caused by nsock using the Lua thread after
> we have killed it (most likely due to timeout). Is there a way to stop
> nsock from doing work on behalf of the thread once we decide to
> destroy the thread?
>
> Cheers,

I can't refute your thread killed on timeout idea however it is likely
that there are other causes for a script to be collected and then used
besides timeouts.  Most of the time the issue happens right in the
middle of a hostgroup before any of the hosts could be timing out.

It even occasionally happens on the first hostgroup so ideas like
memory being corrupted on a previous hostgroup's script timeouts hurting
a later hostgroup can't be the whole story.

Shortly before I had to stop working on this, I was able to catch NSE
hanging in a way that caused 100% CPU usage.  David suggested attaching
GDB to the process.  I printed the size of a lua_State and it was 184
bytes which matches nicely with this Valgrind free message:

> ==12614==  Address 0xa5ab3c8 is 16 bytes inside a block of size 184 free'd

I hope to find the time tomorrow to run a scan with a large host
timeout like 2+ hours.  If I can catch NSE hanging in the middle of a
hostgroup I should have plenty of time to attach GDB and poke around at
the internals.  David has some breakpoints in mind that he'd like to
set and then continue.

Brandon

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