linux-kernel - [PATCH 3.16.y-ckt 015/165] ipv4: ip_check_defrag should not assume that skb_network

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Message-Id: <1427292138-7021-16-git-send-email-luis.henriques@canonical.com>
Date:	Wed, 25 Mar 2015 13:59:48 +0000
From:	Luis Henriques <luis.henriques@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Alexander Drozdov <al.drozdov@...il.com>,
	"David S. Miller" <davem@...emloft.net>,
	Luis Henriques <luis.henriques@...onical.com>
Subject: [PATCH 3.16.y-ckt 015/165] ipv4: ip_check_defrag should not assume that skb_network_offset is zero

3.16.7-ckt9 -stable review patch.  If anyone has any objections, please let me know.

------------------

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

commit 3e32e733d1bbb3f227259dc782ef01d5706bdae0 upstream.

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@...il.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Luis Henriques <luis.henriques@...onical.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 022b5f49aab7..8ff962d15c99 100644
--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -680,27 +680,30 @@ 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))
--
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