ipv4: ip_check_defrag should not assume that skb_network_offset is zero

[ 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>

diff --git a/net/ipv4/ip_fragment.c b/net/ipv4/ip_fragment.c
index fbe920f..16e25a4 100644 (file)
--- 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))