6lowpan: move skb_free from error paths in decompression

Currently we ensure that the skb is freed on every error path in IPHC
decompression which makes it easy to introduce skb leaks.  By centralising
the skb_free into the receive function it makes future decompression routines
easier to maintain.  It does come at the expense of ensuring that the skb
passed into the decompression routine must not be copied.

Signed-off-by: Martin Townsend <mtownsend1973@gmail.com>
Acked-by: Jukka Rissanen <jukka.rissanen@linux.intel.com>
Acked-by: Alexander Aring <alex.aring@gmail.com>
Signed-off-by: Marcel Holtmann <marcel@holtmann.org>

1 files changed, 6 insertions, 10 deletions

diff --git a/net/ieee802154/6lowpan_rtnl.c b/net/ieee802154/6lowpan_rtnl.c
index a96b64c9a73d..290e14f2e92e 100644
--- a/net/ieee802154/6lowpan_rtnl.c
+++ b/net/ieee802154/6lowpan_rtnl.c
@@ -176,13 +176,13 @@ iphc_decompress(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
         raw_dump_table(__func__, "raw skb data dump", skb->data, skb->len);
         /* at least two bytes will be used for the encoding */
         if (skb->len < 2)
-                goto drop;
+                return -EINVAL;
 
         if (lowpan_fetch_skb_u8(skb, &iphc0))
-                goto drop;
+                return -EINVAL;
 
         if (lowpan_fetch_skb_u8(skb, &iphc1))
-                goto drop;
+                return -EINVAL;
 
         ieee802154_addr_to_sa(&sa, &hdr->source);
         ieee802154_addr_to_sa(&da, &hdr->dest);
@@ -200,10 +200,6 @@ iphc_decompress(struct sk_buff *skb, const struct ieee802154_hdr *hdr)
         return lowpan_header_decompress(skb, skb->dev, sap, sa.addr_type,
                                         IEEE802154_ADDR_LEN, dap, da.addr_type,
                                         IEEE802154_ADDR_LEN, iphc0, iphc1);
-
-drop:
-        kfree_skb(skb);
-        return -EINVAL;
 }
 
 static struct sk_buff*
@@ -522,7 +518,7 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
                 case LOWPAN_DISPATCH_IPHC:      /* ipv6 datagram */
                         ret = iphc_decompress(skb, &hdr);
                         if (ret < 0)
-                                goto drop;
+                                goto drop_skb;
 
                         return lowpan_give_skb_to_devices(skb, NULL);
                 case LOWPAN_DISPATCH_FRAG1:     /* first fragment header */
@@ -530,7 +526,7 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
                         if (ret == 1) {
                                 ret = iphc_decompress(skb, &hdr);
                                 if (ret < 0)
-                                        goto drop;
+                                        goto drop_skb;
 
                                 return lowpan_give_skb_to_devices(skb, NULL);
                         } else if (ret == -1) {
@@ -543,7 +539,7 @@ static int lowpan_rcv(struct sk_buff *skb, struct net_device *dev,
                         if (ret == 1) {
                                 ret = iphc_decompress(skb, &hdr);
                                 if (ret < 0)
-                                        goto drop;
+                                        goto drop_skb;
 
                                 return lowpan_give_skb_to_devices(skb, NULL);
                         } else if (ret == -1) {