Re: Dangerous use of alloca

[Samuel Thibault]

Agustina Arzille, on Tue 15 Mar 2016 14:57:19 -0300, wrote:
> On 2016-03-15 13:31, Samuel Thibault wrote:
> >Justus Winter, on Tue 15 Mar 2016 14:39:00 +0100, wrote:
> >>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.
> >
> >What do you mean by "dangerous"?  I don't think we'll ever get a command
> >line that does not fit into the stack.
> 
> That's not what I meant. Stack overflow is clearly very unlikely, if not
> impossible. What I meant about 'dangerous' is the fact that alloca is being
> used inside the list of arguments of a function call,

Sure, I wasn't referring to your use of "dangerous", but Justus' :)

Samuel