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

From: Steffen Klassert
Date: Fri Mar 09 2018 - 08:02:29 EST


On Fri, Mar 09, 2018 at 01:49:07PM +0100, Mathias Krause wrote:
> On 9 March 2018 at 13:21, Andreas Christoforou
> <andreaschristofo@xxxxxxxxx> wrote:
> > The kernel would like to have all stack VLA usage removed[1].
> >
> > Signed-off-by: Andreas Christoforou <andreaschristofo@xxxxxxxxx>
> > ---
> > 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.