Re: Fwd: Segfaulting with Ubuntu

On Friday 05 February 2010 18:43:30 Felix von Leitner wrote:
> > That worked!  What exactly causes this issue? Certainly not a buffer
> > overflow in dietlibc?
>
> I added a workaround to the Makefile.
>
> The issue is this: Ubuntu adds -fstack-protector to the gcc default
> flags, without telling anyone.

They tell you within the ubuntu-adapted version of the man page:

ingo@neo:~$ uname -a
Linux neo 2.6.24-26-server #1 SMP Tue Dec 1 18:26:43 UTC 2009 x86_64 GNU/Linux
ingo@neo:~$ man gcc | grep -A12 -- "-fstack-protector$"
       -fstack-protector
           Emit extra code to check for buffer overflows, such as stack smash‐
           ing attacks.  This is done by adding a guard variable to functions
           with vulnerable objects.  This includes functions that call alloca,
           and functions with buffers larger than 8 bytes.  The guards are
           initialized when a function is entered and then checked when the
           function exits.  If a guard check fails, an error message is
           printed and the program exits.

           NOTE: In Ubuntu 6.10 and later versions this option is enabled by
           default for C, C++, ObjC, ObjC++, if neither -fno-stack-protector
           nor -nostdlib are found.


However, they deserve a kick for turning on any option at all 
that is not the default for a vanilla gcc build...

Regards

Ingo Struck