Re: Dangerous use of alloca

[Agustina Arzille]

Hello, Justus,

On 2016-03-15 10:39, Justus Winter wrote:
> Hi,
>
> Quoting Agustina Arzille (2016-03-15 14:11:27)
> > Hello, everyone.
> >
> > I was browsing some gnumach source files, and noticed some dangerous 
> > use
> > of the gcc builtin 'alloca'. In the file kern/bootstrap.c, lines 212 
> > and
> > 228, we have the following statement:
> >
> > memcpy (alloca (len), ...)
>
> Good catch.  However, alloca is dangerous even if used correctly, and
> is best be avoided.  Would you be so kind to prepare a patch to that
> end?
>
> Thanks,
> Justus

Sure. I will cook up a patch when I get home. Right now, the 
alternatives
to using alloca that I can think of are either:
1) A global buffer with a fixed size, or
2) 'kalloc' and friends.

Obviously, (2) would be the preferred option, but I'm not sure if it's
completely available during bootstrap. What do you guys think?