[PATCH net] netpoll: linearize skb before accessing its data

[Antonio Quartulli <antonio@meshcoding.com>]

__netpoll_rx() assumes that the data buffer of the received
skb is linear and then passes it to rx_hook().
However this is not true because the skb has not been
linearized yet.

This can cause rx_hook() to access non allocated memory
while parsing the received data.

Fix __netpoll_rx() by explicitly linearising the skb.

Signed-off-by: Antonio Quartulli <antonio@meshcoding.com>
---

I checked linux-3.0 and this bug seems to be already there. Please consider
queueing it for stable.


Regards,



 net/core/netpoll.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/net/core/netpoll.c b/net/core/netpoll.c
index fc75c9e..97cff18 100644
--- a/net/core/netpoll.c
+++ b/net/core/netpoll.c
@@ -814,6 +814,9 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
 		if (pskb_trim_rcsum(skb, len))
 			goto out;
 
+		if (skb_linearize(skb))
+			goto out;
+
 		iph = (struct iphdr *)skb->data;
 		if (iph->protocol != IPPROTO_UDP)
 			goto out;
@@ -855,6 +858,8 @@ int __netpoll_rx(struct sk_buff *skb, struct netpoll_info *npinfo)
 			goto out;
 		if (pskb_trim_rcsum(skb, len + sizeof(struct ipv6hdr)))
 			goto out;
+		if (skb_linearize(skb))
+			goto out;
 		ip6h = ipv6_hdr(skb);
 		if (!pskb_may_pull(skb, sizeof(struct udphdr)))
 			goto out;
-- 
1.8.4