[ovs-dev] [PATCH] datapath: Ensure packet length matches headers during checksum setup.

[Jesse Gross]

During the setup of checksumming pointers we need to make sure that
the transport headers are in the skb linear data area.  However, we
don't currently verify that the lengths in the packet headers are
within the size of the packet.  This makes that check before a
BUG() check does it for us.

CC: "Nick Couchman" <Nick.Couchman at seakr.com>
---
 datapath/datapath.c |   23 +++++------------------
 1 files changed, 5 insertions(+), 18 deletions(-)

diff --git a/datapath/datapath.c b/datapath/datapath.c
index 4f74795..83dd76f 100644
--- a/datapath/datapath.c
+++ b/datapath/datapath.c
@@ -551,22 +551,9 @@ void dp_process_received_packet(struct dp_port *p, struct sk_buff *skb)
 }
 
 #if defined(CONFIG_XEN) && defined(HAVE_PROTO_DATA_VALID)
-/* This code is based on a skb_checksum_setup from net/dev/core.c from a
- * combination of Lenny's 2.6.26 Xen kernel and Xen's
- * linux-2.6.18-92.1.10.el5.xs5.0.0.394.644.  We can't call this function
- * directly because it isn't exported in all versions. */
-static int skb_pull_up_to(struct sk_buff *skb, void *ptr)
-{
-	if (ptr < (void *)skb->tail)
-		return 1;
-	if (__pskb_pull_tail(skb,
-			     ptr - (void *)skb->data - skb_headlen(skb))) {
-		return 1;
-	} else {
-		return 0;
-	}
-}
-
+/* This code is based on skb_checksum_setup() from Xen's net/dev/core.c.  We
+ * can't call this function directly because it isn't exported in all
+ * versions. */
 int vswitch_skb_checksum_setup(struct sk_buff *skb)
 {
 	struct iphdr *iph;
@@ -580,7 +567,7 @@ int vswitch_skb_checksum_setup(struct sk_buff *skb)
 	if (skb->protocol != htons(ETH_P_IP))
 		goto out;
 
-	if (!skb_pull_up_to(skb, skb_network_header(skb) + sizeof(struct iphdr)))
+	if (!pskb_may_pull(skb, skb_network_header(skb) + sizeof(struct iphdr) - skb->data))
 		goto out;
 
 	iph = ip_hdr(skb);
@@ -602,7 +589,7 @@ int vswitch_skb_checksum_setup(struct sk_buff *skb)
 		goto out;
 	}
 
-	if (!skb_pull_up_to(skb, th + csum_offset + 2))
+	if (!pskb_may_pull(skb, th + csum_offset + 2 - skb->data))
 		goto out;
 
 	skb->ip_summed = CHECKSUM_PARTIAL;
-- 
1.7.0.4