batman-adv: Linearize fragment packets before merge

We access the data inside the skbs of two fragments directly using memmove
during the merge. The data of the skb could span over multiple skb pages. An
direct access without knowledge about the pages would lead to an invalid memory
access.

Signed-off-by: Sven Eckelmann <sven@narfation.org>
[lindner_marek@yahoo.de: Move return from function to the end]
Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>

diff --git a/net/batman-adv/unicast.c b/net/batman-adv/unicast.c
index ee41fef04b21339868b9726e7f62cd79be741f13..d1a611322549d925ac9123bd02e66367cd6d1da6 100644 (file)
--- a/net/batman-adv/unicast.c
+++ b/net/batman-adv/unicast.c
@@ -50,12 +50,12 @@ static struct sk_buff *frag_merge_packet(struct list_head *head,
                skb = tfp->skb;
        }
 
+       if (skb_linearize(skb) < 0 || skb_linearize(tmp_skb) < 0)
+               goto err;
+
        skb_pull(tmp_skb, sizeof(struct unicast_frag_packet));
-       if (pskb_expand_head(skb, 0, tmp_skb->len, GFP_ATOMIC) < 0) {
-               /* free buffered skb, skb will be freed later */
-               kfree_skb(tfp->skb);
-               return NULL;
-       }
+       if (pskb_expand_head(skb, 0, tmp_skb->len, GFP_ATOMIC) < 0)
+               goto err;
 
        /* move free entry to end */
        tfp->skb = NULL;
@@ -70,6 +70,11 @@ static struct sk_buff *frag_merge_packet(struct list_head *head,
        unicast_packet->packet_type = BAT_UNICAST;
 
        return skb;
+
+err:
+       /* free buffered skb, skb will be freed later */
+       kfree_skb(tfp->skb);
+       return NULL;
 }
 
 static void frag_create_entry(struct list_head *head, struct sk_buff *skb)