Re: [PATCH v2] net: ipv6: xfrm6_state: remove VLA usage

[Steffen Klassert]

On Sat, Mar 10, 2018 at 07:26:44PM +0100, Stefano Brivio wrote:
> On Sat, 10 Mar 2018 09:18:46 -0800
> Kees Cook <keescook@xxxxxxxxxxxx> wrote:
> 
> > On Sat, Mar 10, 2018 at 12:43 AM, Stefano Brivio <sbrivio@xxxxxxxxxx> wrote:
> > > On Sat, 10 Mar 2018 09:40:44 +0200
> > > Andreas Christoforou <andreaschristofo@xxxxxxxxx> wrote:
> > >  
> > >> diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
> > >> index b15075a..270a53a 100644
> > >> --- a/net/ipv6/xfrm6_state.c
> > >> +++ b/net/ipv6/xfrm6_state.c
> > >> @@ -62,7 +62,7 @@ __xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
> > >>  {
> > >>       int i;
> > >>       int class[XFRM_MAX_DEPTH];
> > >> -     int count[maxclass];
> > >> +     int count[XFRM_MAX_DEPTH];
> > >>
> > >>       memset(count, 0, sizeof(count));  
> > >
> > > Can you perhaps initialize 'count' instead of calling memset(), now?  
> > 
> > Do you mean:
> > 
> > int count[XFRM_MAX_DEPTH] = { };
> > 
> > instead of the memset()?
> 
> Yep.
> 
> > I thought the compiler would resolve these both to the same thing?
> 
> Yes, for all practical purposes. With gcc 7.3.0 for x86_64, starting
> from -O1, it's exactly the same. With e.g. gcc 4.4.7, even with -O3,
> they can be a bit different depending on context.
> 
> > The former looks better though! :)
> 
> Yep! :)

If Andreas does a v3 anyway, please also consider to trim the subject
line to something like:

xfrm: remove VLA usage in __xfrm6_sort()