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Subject[PATCH] ipv4: ip_check_defrag should not assume that skb_network_offset is zero
Date
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>
---
net/ipv4/ip_fragment.c | 11 +++++++----
1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index 2c8d98e..145a50c 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -659,27 +659,30 @@ 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))
--
1.9.1


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