ieee802154: 6lowpan: add generic lowpan header check

This patch introduce an earlier check if a 6LoWPAN frame can be valid.
This contains at first for checking if the header contains a dispatch
byte and isn't the nalp dispatch value, which means it isn't a 6LoWPAN
packet. Also we add a check if we can derference the dispatch value by
checking if skb->len is unequal zero.

Reviewed-by: Stefan Schmidt <stefan@osg.samsung.com>
Signed-off-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

diff --git a/net/ieee802154/6lowpan/rx.c b/net/ieee802154/6lowpan/rx.c
index fded109..c46cab3 100644 (file)
--- a/net/ieee802154/6lowpan/rx.c
+++ b/net/ieee802154/6lowpan/rx.c
@@ -15,8 +15,11 @@
 
 #include "6lowpan_i.h"
 
+#define LOWPAN_DISPATCH_FIRST          0xc0
 #define LOWPAN_DISPATCH_FRAG_MASK      0xf8
 
+#define LOWPAN_DISPATCH_NALP           0x00
+
 static int lowpan_give_skb_to_device(struct sk_buff *skb)
 {
        skb->protocol = htons(ETH_P_IPV6);
@@ -162,13 +165,36 @@ rxh_next:
 #undef CALL_RXH
 }
 
+static inline bool lowpan_is_nalp(u8 dispatch)
+{
+       return (dispatch & LOWPAN_DISPATCH_FIRST) == LOWPAN_DISPATCH_NALP;
+}
+
+/* lowpan_rx_h_check checks on generic 6LoWPAN requirements
+ * in MAC and 6LoWPAN header.
+ *
+ * Don't manipulate the skb here, it could be shared buffer.
+ */
+static inline bool lowpan_rx_h_check(struct sk_buff *skb)
+{
+       /* check if we can dereference the dispatch */
+       if (unlikely(!skb->len))
+               return false;
+
+       if (lowpan_is_nalp(*skb_network_header(skb)))
+               return false;
+
+       return true;
+}
+
 static int lowpan_rcv(struct sk_buff *skb, struct net_device *wdev,
                      struct packet_type *pt, struct net_device *orig_wdev)
 {
        struct net_device *ldev;
 
        if (wdev->type != ARPHRD_IEEE802154 ||
-           skb->pkt_type == PACKET_OTHERHOST)
+           skb->pkt_type == PACKET_OTHERHOST ||
+           !lowpan_rx_h_check(skb))
                return NET_RX_DROP;
 
        ldev = wdev->ieee802154_ptr->lowpan_dev;