ipv6: udp: fix the wrong headroom check

commit a9cf73ea7ff78f52662c8658d93c226effbbedde upstream.

At this point, skb->data points to skb_transport_header.
So, headroom check is wrong.

For some case:bridge(UFO is on) + eth device(UFO is off),
there is no enough headroom for IPv6 frag head.
But headroom check is always false.

This will bring about data be moved to there prior to skb->head,
when adding IPv6 frag header to skb.

Signed-off-by: Shan Wei <shanwei@cn.fujitsu.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index be5e5a1a683ec89b77f5ae5ee94b1f7e7890fa95..402a61cd8ef7009bba66ce52385bc4b8dea2be89 100644 (file)
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -1314,7 +1314,7 @@ static struct sk_buff *udp6_ufo_fragment(struct sk_buff *skb, int features)
        skb->ip_summed = CHECKSUM_NONE;
 
        /* Check if there is enough headroom to insert fragment header. */
-       if ((skb_headroom(skb) < frag_hdr_sz) &&
+       if ((skb_mac_header(skb) < skb->head + frag_hdr_sz) &&
            pskb_expand_head(skb, frag_hdr_sz, 0, GFP_ATOMIC))
                goto out;