From b4e3cef703fb21b26db053a770900f2bd910638b Mon Sep 17 00:00:00 2001
From: Li RongQing <roy.qing.li@gmail.com>
Date: Sat, 18 Oct 2014 17:26:04 +0800
Subject: [PATCH] ipv4: fix a potential use after free in gre_offload.c
pskb_may_pull() may change skb->data and make greh pointer oboslete;
so need to reassign greh;
but since first calling pskb_may_pull already ensured that skb->data
has enough space for greh, so move the reference of greh before second
calling pskb_may_pull(), to avoid reassign greh.
Fixes: 7a7ffbabf9("ipv4: fix tunneled VM traffic over hw VXLAN/GRE GSO NIC")
Cc: Wei-Chun Chao <weichunc@plumgrid.com>
Signed-off-by: Li RongQing <roy.qing.li@gmail.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
---
net/ipv4/gre_offload.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/gre_offload.c b/net/ipv4/gre_offload.c
index a777295030716..ccda09628de7e 100644
--- a/net/ipv4/gre_offload.c
+++ b/net/ipv4/gre_offload.c
@@ -55,13 +55,13 @@ static struct sk_buff *gre_gso_segment(struct sk_buff *skb,
if (csum)
skb->encap_hdr_csum = 1;
- if (unlikely(!pskb_may_pull(skb, ghl)))
- goto out;
-
/* setup inner skb. */
skb->protocol = greh->protocol;
skb->encapsulation = 0;
+ if (unlikely(!pskb_may_pull(skb, ghl)))
+ goto out;
+
__skb_pull(skb, ghl);
skb_reset_mac_header(skb);
skb_set_network_header(skb, skb_inner_network_offset(skb));
--
2.30.2