US-CERT Vulnerability Note VU#162289

[Robert C. Seacord]

Andrew,

We'll also add:

-Wstrict-overflow=5

As a work around.  

You are right, I don't regularly read the GCC mailing lists as GCC is not our only concern.  This problem came to our attention because it affected one of your users.  We did consult with Mark before publishing.

rCs


> On Mon, Apr 7, 2008 at 10:28 AM, Robert C. Seacord <rcs@cert.org> wrote:
>   
>>  I believe the vulnerability is that gcc may *silently* discard the overflow
>> checks and that this is a recent change in behavior.
>>     
>
> No it is not recent, unless you consider 1998 recent :).  I don't know
> how many times but we have not changed the behavior of GCC with
> respect of signed integer overflow being undefined.  Since the loop
> optimizers have said this before, we just added an extra pass which
> depends on it more.  I guess you did not read the GCC mailing list
> before posting this Vulnerability because we already discussed this
> many many times before around the time GCC 4.2.0 came out.
>
> Also try -Wstrict-overflow=5 in GCC 4.2.3 and in GCC 4.3.0, we already
> warn about most if not all cases already.
>
> Thanks,
> Andrew Pinski
>   


-- 
Robert C. Seacord
Senior Vulnerability Analyst
CERT/CC 

Work: 412-268-7608
FAX: 412-268-6989