[NETFILTER]: Consistent IP address access in arp_tables.c

Use memcpy just like net/ipv4/arp.c does since
these u32 values can be arbitrarily aligned and
this is not exactly a hot code path.
Signed-off-by: Antti P Miettinen <apm@brigitte.dna.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/ipv4/netfilter/arp_tables.c

@@ -106,7 +106,7 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
 {
 	char *arpptr = (char *)(arphdr + 1);
 	char *src_devaddr, *tgt_devaddr;
-	u32 *src_ipaddr, *tgt_ipaddr;
+	u32 src_ipaddr, tgt_ipaddr;
 	int i, ret;
 
 #define FWINV(bool,invflg) ((bool) ^ !!(arpinfo->invflags & invflg))
@@ -145,11 +145,11 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
 
 	src_devaddr = arpptr;
 	arpptr += dev->addr_len;
-	src_ipaddr = (u32 *) arpptr;
+	memcpy(&src_ipaddr, arpptr, sizeof(u32));
 	arpptr += sizeof(u32);
 	tgt_devaddr = arpptr;
 	arpptr += dev->addr_len;
-	tgt_ipaddr = (u32 *) arpptr;
+	memcpy(&tgt_ipaddr, arpptr, sizeof(u32));
 
 	if (FWINV(arp_devaddr_compare(&arpinfo->src_devaddr, src_devaddr, dev->addr_len),
 		  ARPT_INV_SRCDEVADDR) ||
@@ -160,19 +160,19 @@ static inline int arp_packet_match(const struct arphdr *arphdr,
 		return 0;
 	}
 
-	if (FWINV(((*src_ipaddr) & arpinfo->smsk.s_addr) != arpinfo->src.s_addr,
+	if (FWINV((src_ipaddr & arpinfo->smsk.s_addr) != arpinfo->src.s_addr,
 		  ARPT_INV_SRCIP) ||
-	    FWINV((((*tgt_ipaddr) & arpinfo->tmsk.s_addr) != arpinfo->tgt.s_addr),
+	    FWINV(((tgt_ipaddr & arpinfo->tmsk.s_addr) != arpinfo->tgt.s_addr),
 		  ARPT_INV_TGTIP)) {
 		dprintf("Source or target IP address mismatch.\n");
 
 		dprintf("SRC: %u.%u.%u.%u. Mask: %u.%u.%u.%u. Target: %u.%u.%u.%u.%s\n",
-			NIPQUAD(*src_ipaddr),
+			NIPQUAD(src_ipaddr),
 			NIPQUAD(arpinfo->smsk.s_addr),
 			NIPQUAD(arpinfo->src.s_addr),
 			arpinfo->invflags & ARPT_INV_SRCIP ? " (INV)" : "");
 		dprintf("TGT: %u.%u.%u.%u Mask: %u.%u.%u.%u Target: %u.%u.%u.%u.%s\n",
-			NIPQUAD(*tgt_ipaddr),
+			NIPQUAD(tgt_ipaddr),
 			NIPQUAD(arpinfo->tmsk.s_addr),
 			NIPQUAD(arpinfo->tgt.s_addr),
 			arpinfo->invflags & ARPT_INV_TGTIP ? " (INV)" : "");