[libvirt] [PATCH] Remove ssp buffer size setting

[Michal Privoznik]

On 06.06.2014 11:40, Ján Tomko wrote:
> This option only makes sense with -fstack-protector.
> With -fstack-protector-all, even functions with buffers
> smaller than this are protected.
>
> https://bugzilla.redhat.com/show_bug.cgi?id=1105456
> ---
>   m4/virt-compile-warnings.m4 | 8 --------
>   1 file changed, 8 deletions(-)
>
> diff --git a/m4/virt-compile-warnings.m4 b/m4/virt-compile-warnings.m4
> index 574fbc4..ebc931d 100644
> --- a/m4/virt-compile-warnings.m4
> +++ b/m4/virt-compile-warnings.m4
> @@ -171,14 +171,6 @@ AC_DEFUN([LIBVIRT_COMPILE_WARNINGS],[
>          dnl be great overhead in adding -fstack-protector-all instead
>          dnl wantwarn="$wantwarn -fstack-protector"
>          wantwarn="$wantwarn -fstack-protector-all"
> -       wantwarn="$wantwarn --param=ssp-buffer-size=4"
> -       dnl Even though it supports it, clang complains about
> -       dnl use of --param=ssp-buffer-size=4 unless used with
> -       dnl the -c arg. It doesn't like it when used with args
> -       dnl that just link together .o files. Unfortunately
> -       dnl we can't avoid that with automake, so we must turn
> -       dnl off the following clang specific warning
> -       wantwarn="$wantwarn -Wno-unused-command-line-argument"
>          ;;
>          *-*-freebsd*)
>          dnl FreeBSD ships old gcc 4.2.1 which doesn't handle
>

 From the gcc man page:

        -fstack-protector
            Emit extra code to check for buffer overflows, such as stack 
smashing 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.

        -fstack-protector-all
            Like -fstack-protector except that all functions are protected.


So when using -fstack-protector-all even functions with 4B buffers are 
protected.

ACK

Michal