Re: Commit: Use of alloca considered dangerous

[Jeff Law <law at redhat dot com>]

On 03/21/2016 10:56 AM, Paul_Koning@Dell.com wrote:
> > On Mar 21, 2016, at 12:30 PM, Nick Clifton <nickc@redhat.com> wrote:
> >
> > Hi Guys,
> >
> >   It was pointed out to me the other day that there are some unbounded
> >   calls to alloca in the binutils, which in theory could lead to
> >   exploits.  So I tried adding -Wstack-usage=NNN to the command line and
> >   discovered that gcc would complain about any use of alloca, even
> >   bounded ones.  Still they were easy to fix, and removing the use of
> >   alloca, and variable length local arrays as well, seems like a good
> >   idea.
>
> I agree that alloca() needs bounds checks, but I don't see why you say that avoiding alloca entirely is "a good idea".
Based on what I've seen through the years, if you can't put a hard 
bounds on an alloca, then you're far better off from a security 
standpoint avoiding it completely.

jeff