arcnet: provide a buffer big enough to actually receive packets

struct archdr is only big enough to hold the header of various types of
arcnet packets. So to provide enough space to hold the data read from
hardware provide a buffer large enough to hold a packet with maximal
size.

The problem was noticed by the stack protector which makes the kernel
oops.

Signed-off-by: Uwe Kleine-König <[e-mail]>
Acked-by: Michael Grzeschik <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

drivers/net/arcnet/arcnet.c

···
 static void arcnet_rx(struct net_device *dev, int bufnum)
 {
 	struct arcnet_local *lp = netdev_priv(dev);
-	struct archdr pkt;
+	union {
+		struct archdr pkt;
+		char buf[512];
+	} rxdata;
 	struct arc_rfc1201 *soft;
 	int length, ofs;
 
-	soft = &pkt.soft.rfc1201;
+	soft = &rxdata.pkt.soft.rfc1201;
 
-	lp->hw.copy_from_card(dev, bufnum, 0, &pkt, ARC_HDR_SIZE);
-	if (pkt.hard.offset[0]) {
-		ofs = pkt.hard.offset[0];
+	lp->hw.copy_from_card(dev, bufnum, 0, &rxdata.pkt, ARC_HDR_SIZE);
+	if (rxdata.pkt.hard.offset[0]) {
+		ofs = rxdata.pkt.hard.offset[0];
 		length = 256 - ofs;
 	} else {
-		ofs = pkt.hard.offset[1];
+		ofs = rxdata.pkt.hard.offset[1];
 		length = 512 - ofs;
 	}
 
 	/* get the full header, if possible */
-	if (sizeof(pkt.soft) <= length) {
-		lp->hw.copy_from_card(dev, bufnum, ofs, soft, sizeof(pkt.soft));
+	if (sizeof(rxdata.pkt.soft) <= length) {
+		lp->hw.copy_from_card(dev, bufnum, ofs, soft, sizeof(rxdata.pkt.soft));
 	} else {
-		memset(&pkt.soft, 0, sizeof(pkt.soft));
+		memset(&rxdata.pkt.soft, 0, sizeof(rxdata.pkt.soft));
 		lp->hw.copy_from_card(dev, bufnum, ofs, soft, length);
 	}
 
 	arc_printk(D_DURING, dev, "Buffer #%d: received packet from %02Xh to %02Xh (%d+4 bytes)\n",
-		   bufnum, pkt.hard.source, pkt.hard.dest, length);
+		   bufnum, rxdata.pkt.hard.source, rxdata.pkt.hard.dest, length);
 
 	dev->stats.rx_packets++;
 	dev->stats.rx_bytes += length + ARC_HDR_SIZE;
···
 	if (arc_proto_map[soft->proto]->is_ip) {
 		if (BUGLVL(D_PROTO)) {
 			struct ArcProto
-			*oldp = arc_proto_map[lp->default_proto[pkt.hard.source]],
+			*oldp = arc_proto_map[lp->default_proto[rxdata.pkt.hard.source]],
 			*newp = arc_proto_map[soft->proto];
 
 			if (oldp != newp) {
 				arc_printk(D_PROTO, dev,
 					   "got protocol %02Xh; encap for host %02Xh is now '%c' (was '%c')\n",
-					   soft->proto, pkt.hard.source,
+					   soft->proto, rxdata.pkt.hard.source,
 					   newp->suffix, oldp->suffix);
 			}
 		}
···
 		lp->default_proto[0] = soft->proto;
 
 		/* in striking contrast, the following isn't a hack. */
-		lp->default_proto[pkt.hard.source] = soft->proto;
+		lp->default_proto[rxdata.pkt.hard.source] = soft->proto;
 	}
 	/* call the protocol-specific receiver. */
-	arc_proto_map[soft->proto]->rx(dev, bufnum, &pkt, length);
+	arc_proto_map[soft->proto]->rx(dev, bufnum, &rxdata.pkt, length);
 }
 
 static void null_rx(struct net_device *dev, int bufnum,