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Date: Mon, 12 Mar 2018 13:24:03 +0100
From: Steffen Klassert <steffen.klassert@...unet.com>
To: Stefano Brivio <sbrivio@...hat.com>
CC: Kees Cook <keescook@...omium.org>, Andreas Christoforou
<andreaschristofo@...il.com>, Kernel Hardening
<kernel-hardening@...ts.openwall.com>, Herbert Xu
<herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>,
Alexey Kuznetsov <kuznet@....inr.ac.ru>, Hideaki YOSHIFUJI
<yoshfuji@...ux-ipv6.org>, Network Development <netdev@...r.kernel.org>, LKML
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2] net: ipv6: xfrm6_state: remove VLA usage
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@...omium.org> wrote:
>
> > On Sat, Mar 10, 2018 at 12:43 AM, Stefano Brivio <sbrivio@...hat.com> wrote:
> > > On Sat, 10 Mar 2018 09:40:44 +0200
> > > Andreas Christoforou <andreaschristofo@...il.com> 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()
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