Fuzzing elfutils

Alexander Cherepanov cherepan at mccme.ru
Sun Dec 21 22:20:24 UTC 2014

On 2014-12-19 03:13, Mark Wielaard wrote:
> On Thu, 2014-12-18 at 21:15 +0300, Alexander Cherepanov wrote:
>>> Thanks. I'll try to reproduce them soon. But without a general leb128
>>> length check fix using eu-readelf -w might be somewhat unreliable (and
>>> this also might impact -e/--exceptions).
>> There are many patches flowing and it's not clear which are relevant for
>> my crashes and when it's the right time to start fuzzing again.
> Now would be a good time :)


> I am not aware of any pending crashers.
> Although I am aware of 3 areas that still need some work because they
> could potentially cause crashes on bad input (I'll update the bug soon).

It seems the crashes I uploaded yesterday hit at least one of these 
areas (Dwarf_Abbrev) but maybe not others. OTOH you don't need fuzzing 
to hit these areas if you already know they are problematic. Fuzzing is 
more interesting when it uncovers something unexpected.

> Sorry there were so many changes. But sadly there were a lot of
> crashers. I hope we got them all. And some of yours needed some more
> general fixes that needed some discussion. But those patches are now
> finally all in.

The amount of fixes is not something to be sorry about, it's something 
to be proud of:-)

But it would be nice to have an idea which commits fix which crashes. 
Your first commit (d0070a9) included Reported-by: -- thanks! But it was 
the only such commit, then it was not clear whether you fix further 
crashes from the same bunch or fix completely different crashes.

I guess I can formulate two wishes now:
- to include Reported-by: tag in your commits (to make it possible to 
track progress and as a credit);
- to let me know when it's reasonable to start next round of fuzzing.

>> Further fuzzing found 3 crashes in readelf. Not sure if you want to look
>> into them now.
> Yes, please do add them to the "fuzzer crash bug":
> https://bugzilla.redhat.com/show_bug.cgi?id=1170810


> Sorry if they don't get immediately fixed for 0.161. But the release
> should already have happened and I like to include just some testsuite
> cleanups and get it shipped, before continuing with more work.

Sure, trying to fix everything will postpone the release indefinitely:-(

Alexander Cherepanov

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