2018-03-09 12:23:16

by Andreas Christoforou

Subject: [PATCH] net: ipv6: xfrm6_state: remove VLA usage

The kernel would like to have all stack VLA usage removed[1].

Signed-off-by: Andreas Christoforou <[email protected]>
---
net/ipv6/xfrm6_state.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
index b15075a..45c0d98 100644
--- a/net/ipv6/xfrm6_state.c
+++ b/net/ipv6/xfrm6_state.c
@@ -62,7 +62,12 @@ __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;
+
+ count = kcalloc(maxclass + 1, sizeof(*count), GFP_KERNEL);
+
+ if (!count)
+ return -ENOMEM;

memset(count, 0, sizeof(count));

@@ -80,6 +85,7 @@ __xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
src[i] = NULL;
}

+ kfree(count);
return 0;
}

--
2.7.4

2018-03-09 12:37:00

by Steffen Klassert

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

On Fri, Mar 09, 2018 at 02:21:46PM +0200, Andreas Christoforou wrote:
> The kernel would like to have all stack VLA usage removed[1].
>
> Signed-off-by: Andreas Christoforou <[email protected]>

Can you please explain why you want this change?

2018-03-09 12:50:18

by Mathias Krause

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

On 9 March 2018 at 13:21, Andreas Christoforou
<[email protected]> wrote:
> The kernel would like to have all stack VLA usage removed[1].
>
> Signed-off-by: Andreas Christoforou <[email protected]>
> ---
> net/ipv6/xfrm6_state.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
> index b15075a..45c0d98 100644
> --- a/net/ipv6/xfrm6_state.c
> +++ b/net/ipv6/xfrm6_state.c
> @@ -62,7 +62,12 @@ __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;
> +
> + count = kcalloc(maxclass + 1, sizeof(*count), GFP_KERNEL);
> +
> + if (!count)
> + return -ENOMEM;
>
> memset(count, 0, sizeof(count));
>
> @@ -80,6 +85,7 @@ __xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
> src[i] = NULL;
> }
>
> + kfree(count);
> return 0;
> }

Instead of dynamically allocating and freeing memory here, shouldn't
we just get rid of the maxclass parameter and use XFRM_MAX_DEPTH as
size for the count[] array, too?

Cheers,
Mathias

2018-03-09 13:04:32

by Steffen Klassert

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

On Fri, Mar 09, 2018 at 01:49:07PM +0100, Mathias Krause wrote:
> On 9 March 2018 at 13:21, Andreas Christoforou
> <[email protected]> wrote:
> > The kernel would like to have all stack VLA usage removed[1].
> >
> > Signed-off-by: Andreas Christoforou <[email protected]>
> > ---
> > net/ipv6/xfrm6_state.c | 8 +++++++-
> > 1 file changed, 7 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
> > index b15075a..45c0d98 100644
> > --- a/net/ipv6/xfrm6_state.c
> > +++ b/net/ipv6/xfrm6_state.c
> > @@ -62,7 +62,12 @@ __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;
> > +
> > + count = kcalloc(maxclass + 1, sizeof(*count), GFP_KERNEL);
> > +
> > + if (!count)
> > + return -ENOMEM;
> >
> > memset(count, 0, sizeof(count));
> >
> > @@ -80,6 +85,7 @@ __xfrm6_sort(void **dst, void **src, int n, int (*cmp)(void *p), int maxclass)
> > src[i] = NULL;
> > }
> >
> > + kfree(count);
> > return 0;
> > }
>
> Instead of dynamically allocating and freeing memory here, shouldn't
> we just get rid of the maxclass parameter and use XFRM_MAX_DEPTH as
> size for the count[] array, too?

Right, that's the way to go. Aside from that, allocating
with GFP_KERNEL is definitely wrong here.

2018-03-09 18:36:49

by Sergei Shtylyov

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

Hello!

On 03/09/2018 03:21 PM, Andreas Christoforou wrote:

> The kernel would like to have all stack VLA usage removed[1].
>
> Signed-off-by: Andreas Christoforou <[email protected]>
> ---
> net/ipv6/xfrm6_state.c | 8 +++++++-
> 1 file changed, 7 insertions(+), 1 deletion(-)
>
> diff --git a/net/ipv6/xfrm6_state.c b/net/ipv6/xfrm6_state.c
> index b15075a..45c0d98 100644
> --- a/net/ipv6/xfrm6_state.c
> +++ b/net/ipv6/xfrm6_state.c
> @@ -62,7 +62,12 @@ __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;
> +
> + count = kcalloc(maxclass + 1, sizeof(*count), GFP_KERNEL);
> +

Empty line not needed here.

> + if (!count)
> + return -ENOMEM;
>
> memset(count, 0, sizeof(count));
>
[...]

MBR, Sergei