netfilter: nf_ct_h323: Out Of Bound Read in Netfilter Conntrack

Add missing counter decrement to prevent out of bounds memory read.
Signed-off-by: Eric Sesterhenn <eric.sesterhenn@x41-dsec.de>
Acked-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_conntrack_h323_asn1.c

@@ -877,6 +877,7 @@ int DecodeQ931(unsigned char *buf, size_t sz, Q931 *q931)
 		if (sz < 1)
 			break;
 		len = *p++;
+		sz--;
 		if (sz < len)
 			break;
 		p += len;