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Date: Wed, 25 Apr 2018 11:11:47 +0200
From: Stefano Brivio <sbrivio@...hat.com>
To: Kees Cook <keescook@...omium.org>
Cc: Andreas Christoforou <andreaschristofo@...il.com>,
kernel-hardening@...ts.openwall.com, Steffen Klassert
<steffen.klassert@...unet.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>,
netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 ipsec-next] xfrm: remove VLA usage in __xfrm6_sort()
Hi Kees,
On Tue, 24 Apr 2018 16:46:51 -0700
Kees Cook <keescook@...omium.org> wrote:
> In the quest to remove all stack VLA usage removed from the kernel[1],
> just use XFRM_MAX_DEPTH as already done for the "class" array. In one
> case, it'll do this loop up to 5, the other caller up to 6.
>
> [1] https://lkml.org/lkml/2018/3/7/621
>
> Co-developed-by: Andreas Christoforou <andreaschristofo@...il.com>
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> v3:
> - adjust Subject and commit log (Steffen)
> - use "= { }" instead of memset() (Stefano)
> - reorder variables (Stefano)
> v2:
> - use XFRM_MAX_DEPTH for "count" array (Steffen and Mathias).
> ---
> net/ipv6/xfrm6_state.c | 4 ++--
> 1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
> index 16f434791763..eeb44b64ae7f 100644
> --- a/net/ipv6/xfrm6_state.c
> +++ b/net/ipv6/xfrm6_state.c
> @@ -60,9 +60,9 @@ xfrm6_init_temprop(struct xfrm_state *x, const struct xfrm_tmpl *tmpl,
> static int
> __xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
> {
> - int i;
> + int count[XFRM_MAX_DEPTH] = { };
> int class[XFRM_MAX_DEPTH];
> - int count[maxclass];
> + int i;
>
> memset(count, 0, sizeof(count));
I guess you forgot to remove the memset() here. Just to be clear, I
think this is how it should look like:
--- a/net/ipv6/xfrm6_state.c
+++ b/net/ipv6/xfrm6_state.c
@@ -60,11 +60,9 @@ xfrm6_init_temprop(struct xfrm_state *x, const struct xfrm_tmpl *tmpl,
static int
__xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
{
- int i;
+ int count[XFRM_MAX_DEPTH] = { };
int class[XFRM_MAX_DEPTH];
- int count[maxclass];
-
- memset(count, 0, sizeof(count));
+ int i;
for (i = 0; i < n; i++) {
int c;
--
Stefano
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