[-mainline] netfilter: ipset: small potential read beyond the end of buffer

We could be reading 8 bytes into a 4 byte buffer here.  It seems
harmless but adding a check is the right thing to do and it silences a
static checker warning.

Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

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On Fri, Nov 07, 2014 at 09:21:40AM +0300, Dan Carpenter wrote:
> We could be reading 8 bytes into a 4 byte buffer here.  It seems
> harmless but adding a check is the right thing to do and it silences a
> static checker warning.
> 
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> 
> diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
> index 86f9d76..ac08a3f 100644
> --- a/net/netfilter/ipset/ip_set_core.c
> +++ b/net/netfilter/ipset/ip_set_core.c
> @@ -1863,7 +1863,8 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
>  	if (*op < IP_SET_OP_VERSION) {
>  		/* Check the version at the beginning of operations */
>  		struct ip_set_req_version *req_version = data;
> -		if (req_version->version != IPSET_PROTOCOL) {
> +		if (*len < sizeof(struct ip_set_req_version) ||
> +		    req_version->version != IPSET_PROTOCOL) {
>  			ret = -EPROTO;
>  			goto done;

Thanks for catching up this.

From other similar code in that location, I can see Jozsef is using
this pattern:

                if (*len != sizeof(struct ip_set_req_version)) {
                        ret = -EINVAL;
                        goto done;
                }

I think it would be good to stick to that for consistency. Thanks.
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On Mon, 10 Nov 2014, Pablo Neira Ayuso wrote:

> On Fri, Nov 07, 2014 at 09:21:40AM +0300, Dan Carpenter wrote:
> > We could be reading 8 bytes into a 4 byte buffer here.  It seems
> > harmless but adding a check is the right thing to do and it silences a
> > static checker warning.
> > 
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > 
> > diff --git a/net/netfilter/ipset/ip_set_core.c b/net/netfilter/ipset/ip_set_core.c
> > index 86f9d76..ac08a3f 100644
> > --- a/net/netfilter/ipset/ip_set_core.c
> > +++ b/net/netfilter/ipset/ip_set_core.c
> > @@ -1863,7 +1863,8 @@ ip_set_sockfn_get(struct sock *sk, int optval, void __user *user, int *len)
> >  	if (*op < IP_SET_OP_VERSION) {
> >  		/* Check the version at the beginning of operations */
> >  		struct ip_set_req_version *req_version = data;
> > -		if (req_version->version != IPSET_PROTOCOL) {
> > +		if (*len < sizeof(struct ip_set_req_version) ||
> > +		    req_version->version != IPSET_PROTOCOL) {
> >  			ret = -EPROTO;
> >  			goto done;
> 
> Thanks for catching up this.
> 
> >From other similar code in that location, I can see Jozsef is using
> this pattern:
> 
>                 if (*len != sizeof(struct ip_set_req_version)) {
>                         ret = -EINVAL;
>                         goto done;
>                 }
> 
> I think it would be good to stick to that for consistency. Thanks.

Absolutely, yes.

Acked-by: Jozsef Kadlecsik <kadlec@blackhole.kfki.hu>

Best regards,
Jozsef
-
E-mail  : kadlec@blackhole.kfki.hu, kadlecsik.jozsef@wigner.mta.hu
PGP key : http://www.kfki.hu/~kadlec/pgp_public_key.txt
Address : Wigner Research Centre for Physics, Hungarian Academy of Sciences
          H-1525 Budapest 114, POB. 49, Hungary
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