Re: [perl #119505] Segfault from bad backreference

[Salvatore Bonaccorso <carnil () debian org>]

Hi Kurt,

On Fri, Jan 23, 2015 at 02:38:51PM -0700, Kurt Seifried wrote:
> http://perl5.git.perl.org/perl.git/commitdiff/0c2990d652e985784f095bba4bc356481a66aa06
>
> The code that parses regex backrefs (or ambiguous backref/octal) such as
> \123, did a simple atoi(), which could wrap round to negative values on
> long digit strings and cause seg faults.
>
> Include a check on the length of the digit string, and if greater than 9
> digits, assume it can never be a valid backref (obviating the need for
> the atoi() call).
>
> I've also simplified the code a bit, putting most of the \g handling
> code into a single block, rather than doing multiple "if (isg) {...}".
>
> PoC:
>
> https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=776046
> perl -e '/\7777777777/'
>
> not sure if this can be exploited at all, but someone creative maybe has
> ideas, if so this may need a CVE.

Just additional infomration: I think this was way back found already
around 2008, in opensuse-commits the following can be found:

http://marc.info/?l=opensuse-commit&m=121933719424130

then also reported in the Perl request-tracker at

https://rt.perl.org/Public/Bug/Display.html?id=119505

Regards,
Salvatore