[PATCH 3.2 093/110] inet: frags: fix defragmented packet's IP header for af_packet

[Ben Hutchings]

3.2.71-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Edward Hyunkoo Jee <edjee@xxxxxxxxxx>

commit 0848f6428ba3a2e42db124d41ac6f548655735bf upstream.

When ip_frag_queue() computes positions, it assumes that the passed
sk_buff does not contain L2 headers.

However, when PACKET_FANOUT_FLAG_DEFRAG is used, IP reassembly
functions can be called on outgoing packets that contain L2 headers.

Also, IPv4 checksum is not corrected after reassembly.

Fixes: 7736d33f4262 ("packet: Add pre-defragmentation support for ipv4 fanouts.")
Signed-off-by: Edward Hyunkoo Jee <edjee@xxxxxxxxxx>
Signed-off-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Cc: Jerry Chu <hkchu@xxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/ipv4/ip_fragment.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/net/ipv4/ip_fragment.c
+++ b/net/ipv4/ip_fragment.c
@@ -385,7 +385,7 @@ static int ip_frag_queue(struct ipq *qp,
 	ihl = ip_hdrlen(skb);
 
 	/* Determine the position of this fragment. */
-	end = offset + skb->len - ihl;
+	end = offset + skb->len - skb_network_offset(skb) - ihl;
 	err = -EINVAL;
 
 	/* Is this the final fragment? */
@@ -415,7 +415,7 @@ static int ip_frag_queue(struct ipq *qp,
 		goto err;
 
 	err = -ENOMEM;
-	if (pskb_pull(skb, ihl) == NULL)
+	if (!pskb_pull(skb, skb_network_offset(skb) + ihl))
 		goto err;
 
 	err = pskb_trim_rcsum(skb, end - offset);
@@ -638,6 +638,8 @@ static int ip_frag_reasm(struct ipq *qp,
 	iph->frag_off = 0;
 	iph->tot_len = htons(len);
 	iph->tos |= ecn;
+	ip_send_check(iph);
+
 	IP_INC_STATS_BH(net, IPSTATS_MIB_REASMOKS);
 	qp->q.fragments = NULL;
 	qp->q.fragments_tail = NULL;

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