arcnet: provide a buffer big enough to actually receive packets

BugLink: https://bugs.launchpad.net/bugs/1848589

[ Upstream commit 108639aac35eb57f1d0e8333f5fc8c7ff68df938 ]

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 <u.kleine-koenig@pengutronix.de>
Acked-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Connor Kuehl <connor.kuehl@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

drivers/net/arcnet/arcnet.c

@@ -1009,31 +1009,34 @@ EXPORT_SYMBOL(arcnet_interrupt);
 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;
@@ -1042,13 +1045,13 @@ static void arcnet_rx(struct net_device *dev, int bufnum)
 	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);
 			}
 		}
@@ -1057,10 +1060,10 @@ static void arcnet_rx(struct net_device *dev, int bufnum)
 		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,