2018-04-24 23:48:24

by Kees Cook

Subject: [PATCH v3 ipsec-next] xfrm: remove VLA usage in __xfrm6_sort()

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 <[email protected]>
Signed-off-by: Kees Cook <[email protected]>
---
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));

--
2.7.4


--
Kees Cook
Pixel Security

2018-04-25 09:13:28

by Stefano Brivio

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 <[email protected]> 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 <[email protected]>
> Signed-off-by: Kees Cook <[email protected]>
> ---
> 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