[PATCH 3.13.y-ckt 07/96] ipv4: fix a potential use after free in ip_tunnel_core.c

From: Kamal Mostafa
Date: Mon Dec 15 2014 - 14:50:22 EST

3.13.11-ckt13 -stable review patch. If anyone has any objections, please let me know.


From: Li RongQing <roy.qing.li@xxxxxxxxx>

[ Upstream commit 1245dfc8cadb258386fcd27df38215a0eccb1f17 ]

pskb_may_pull() maybe change skb->data and make eth pointer oboslete,
so set eth after pskb_may_pull()

Fixes:3d7b46cd("ip_tunnel: push generic protocol handling to ip_tunnel module")
Cc: Pravin B Shelar <pshelar@xxxxxxxxxx>
Signed-off-by: Li RongQing <roy.qing.li@xxxxxxxxx>
Acked-by: Pravin B Shelar <pshelar@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
net/ipv4/ip_tunnel_core.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/net/ipv4/ip_tunnel_core.c b/net/ipv4/ip_tunnel_core.c
index 67bd005..e67e4be 100644
--- a/net/ipv4/ip_tunnel_core.c
+++ b/net/ipv4/ip_tunnel_core.c
@@ -91,11 +91,12 @@ int iptunnel_pull_header(struct sk_buff *skb, int hdr_len, __be16 inner_proto)
skb_pull_rcsum(skb, hdr_len);

if (inner_proto == htons(ETH_P_TEB)) {
- struct ethhdr *eh = (struct ethhdr *)skb->data;
+ struct ethhdr *eh;

if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
return -ENOMEM;

+ eh = (struct ethhdr *)skb->data;
if (likely(ntohs(eh->h_proto) >= ETH_P_802_3_MIN))
skb->protocol = eh->h_proto;

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