[PATCH 3.2 193/221] ipv4: ip_check_defrag should not assume that skb_network_offset is zero

Ben Hutchings
2015-05-05T02:24:11Z

From: Alexander Drozdov <al.drozdov@gmail.com>

[ Upstream commit 3e32e733d1bbb3f227259dc782ef01d5706bdae0 ]

ip_check_defrag() may be used by af_packet to defragment outgoing packets.
skb_network_offset() of af_packet's outgoing packets is not zero.

Signed-off-by: Alexander Drozdov <al.drozdov@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
net/ipv4/ip_fragment.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -692,27 +692,30 @@ EXPORT_SYMBOL(ip_defrag);
struct sk_buff *ip_check_defrag(struct sk_buff *skb, u32 user)
{
struct iphdr iph;
+ int netoff;
u32 len;

if (skb->protocol != htons(ETH_P_IP))
return skb;

- if (skb_copy_bits(skb, 0, &iph, sizeof(iph)) < 0)
+ netoff = skb_network_offset(skb);
+
+ if (skb_copy_bits(skb, netoff, &iph, sizeof(iph)) < 0)
return skb;

if (iph.ihl < 5 || iph.version != 4)
return skb;

len = ntohs(iph.tot_len);
- if (skb->len < len || len < (iph.ihl * 4))
+ if (skb->len < netoff + len || len < (iph.ihl * 4))
return skb;

if (ip_is_fragment(&iph)) {
skb = skb_share_check(skb, GFP_ATOMIC);
if (skb) {
- if (!pskb_may_pull(skb, iph.ihl*4))
+ if (!pskb_may_pull(skb, netoff + iph.ihl * 4))
return skb;
- if (pskb_trim_rcsum(skb, len))
+ if (pskb_trim_rcsum(skb, netoff + len))
return skb;
memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
if (ip_defrag(skb, user))