ipvlan: Fix insufficient skb linear check for arp

In the function ipvlan_get_L3_hdr, current codes use pskb_may_pull to
make sure the skb header has enough linear room for arp header. But it
would access the arp payload in func ipvlan_addr_lookup. So it still may
access the unepxected memory.

Now use arp_hdr_len(port->dev) instead of the arp header as the param.
Signed-off-by: NGao Feng <gfree.wind@vip.163.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ipvlan/ipvlan_core.c

@@ -116,7 +116,7 @@ bool ipvlan_addr_busy(struct ipvl_port *port, void *iaddr, bool is_v6)
 	return false;
 }
 
-static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
+static void *ipvlan_get_L3_hdr(struct ipvl_port *port, struct sk_buff *skb, int *type)
 {
 	void *lyr3h = NULL;
 
@@ -124,7 +124,7 @@ static void *ipvlan_get_L3_hdr(struct sk_buff *skb, int *type)
 	case htons(ETH_P_ARP): {
 		struct arphdr *arph;
 
-		if (unlikely(!pskb_may_pull(skb, sizeof(*arph))))
+		if (unlikely(!pskb_may_pull(skb, arp_hdr_len(port->dev))))
 			return NULL;
 
 		arph = arp_hdr(skb);
@@ -510,7 +510,7 @@ static int ipvlan_xmit_mode_l3(struct sk_buff *skb, struct net_device *dev)
 	struct ipvl_addr *addr;
 	int addr_type;
 
-	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	lyr3h = ipvlan_get_L3_hdr(ipvlan->port, skb, &addr_type);
 	if (!lyr3h)
 		goto out;
 
@@ -539,7 +539,7 @@ static int ipvlan_xmit_mode_l2(struct sk_buff *skb, struct net_device *dev)
 
 	if (!ipvlan_is_vepa(ipvlan->port) &&
 	    ether_addr_equal(eth->h_dest, eth->h_source)) {
-		lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+		lyr3h = ipvlan_get_L3_hdr(ipvlan->port, skb, &addr_type);
 		if (lyr3h) {
 			addr = ipvlan_addr_lookup(ipvlan->port, lyr3h, addr_type, true);
 			if (addr) {
@@ -606,7 +606,7 @@ static bool ipvlan_external_frame(struct sk_buff *skb, struct ipvl_port *port)
 	int addr_type;
 
 	if (ether_addr_equal(eth->h_source, skb->dev->dev_addr)) {
-		lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+		lyr3h = ipvlan_get_L3_hdr(port, skb, &addr_type);
 		if (!lyr3h)
 			return true;
 
@@ -627,7 +627,7 @@ static rx_handler_result_t ipvlan_handle_mode_l3(struct sk_buff **pskb,
 	struct sk_buff *skb = *pskb;
 	rx_handler_result_t ret = RX_HANDLER_PASS;
 
-	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	lyr3h = ipvlan_get_L3_hdr(port, skb, &addr_type);
 	if (!lyr3h)
 		goto out;
 
@@ -666,7 +666,7 @@ static rx_handler_result_t ipvlan_handle_mode_l2(struct sk_buff **pskb,
 	} else {
 		struct ipvl_addr *addr;
 
-		lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+		lyr3h = ipvlan_get_L3_hdr(port, skb, &addr_type);
 		if (!lyr3h)
 			return ret;
 
@@ -717,7 +717,7 @@ static struct ipvl_addr *ipvlan_skb_to_addr(struct sk_buff *skb,
 	if (!port || port->mode != IPVLAN_MODE_L3S)
 		goto out;
 
-	lyr3h = ipvlan_get_L3_hdr(skb, &addr_type);
+	lyr3h = ipvlan_get_L3_hdr(port, skb, &addr_type);
 	if (!lyr3h)
 		goto out;