[IPX]: Another nonlinear receive fix

Need to check some more cases in IPX receive.  If the skb is purely
fragments, the IPX header needs to be extracted. The function
pskb_may_pull() may in theory invalidate all the pointers in the skb,
so references to ipx header must be refreshed.

Signed-off-by: Stephen Hemminger <shemminger@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 2 deletions

diff --git a/net/ipx/af_ipx.c b/net/ipx/af_ipx.c
index c13e86b14f69..401964204866 100644
--- a/net/ipx/af_ipx.c
+++ b/net/ipx/af_ipx.c
@@ -1642,14 +1642,17 @@ static int ipx_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_ty
         if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
                 goto out;
 
-        ipx             = ipx_hdr(skb);
-        ipx_pktsize     = ntohs(ipx->ipx_pktsize);
+        if (!pskb_may_pull(skb, sizeof(struct ipxhdr)))
+                goto drop;
+
+        ipx_pktsize = ntohs(ipxhdr(skb)->ipx_pktsize);
         
         /* Too small or invalid header? */
         if (ipx_pktsize < sizeof(struct ipxhdr) ||
             !pskb_may_pull(skb, ipx_pktsize))
                 goto drop;
                         
+        ipx = ipx_hdr(skb);
         if (ipx->ipx_checksum != IPX_NO_CHECKSUM &&
            ipx->ipx_checksum != ipx_cksum(ipx, ipx_pktsize))
                 goto drop;