ah: reload pointers to skb data after calling skb_cow_data()

skb_cow_data() may allocate a new data buffer, so pointers on
skb should be set after this function.

Bug was introduced by commit dff3bb06 ("ah4: convert to ahash")
and 8631e9bd ("ah6: convert to ahash").

Signed-off-by: Wang Xuefu <xuefu.wang@6wind.com>
Acked-by: Krzysztof Witek <krzysztof.witek@6wind.com>
Signed-off-by: Nicolas Dichtel <nicolas.dichtel@6wind.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 5 insertions, 3 deletions

diff --git a/net/ipv6/ah6.c b/net/ipv6/ah6.c
index ee82d4ef26ce..1aba54ae53c4 100644
--- a/net/ipv6/ah6.c
+++ b/net/ipv6/ah6.c
@@ -538,14 +538,16 @@ static int ah6_input(struct xfrm_state *x, struct sk_buff *skb)
         if (!pskb_may_pull(skb, ah_hlen))
                 goto out;
 
-        ip6h = ipv6_hdr(skb);
-
-        skb_push(skb, hdr_len);
 
         if ((err = skb_cow_data(skb, 0, &trailer)) < 0)
                 goto out;
         nfrags = err;
 
+        ah = (struct ip_auth_hdr *)skb->data;
+        ip6h = ipv6_hdr(skb);
+
+        skb_push(skb, hdr_len);
+
         work_iph = ah_alloc_tmp(ahash, nfrags, hdr_len + ahp->icv_trunc_len);
         if (!work_iph)
                 goto out;