[PATCH] net/ipv6: Fix CALIPSO causing GPF with datagram support

[Richard Haines]

When using CALIPSO with IPPROTO_UDP it is possible to trigger a GPF as the
IP header may have moved.

Also update the payload length after adding the CALIPSO option.

Signed-off-by: Richard Haines <richard_c_hai...@btinternet.com>
---
 net/ipv6/calipso.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/calipso.c b/net/ipv6/calipso.c
index 37ac9de..8d772fe 100644
--- a/net/ipv6/calipso.c
+++ b/net/ipv6/calipso.c
@@ -1319,7 +1319,7 @@ static int calipso_skbuff_setattr(struct sk_buff *skb,
        struct ipv6hdr *ip6_hdr;
        struct ipv6_opt_hdr *hop;
        unsigned char buf[CALIPSO_MAX_BUFFER];
-       int len_delta, new_end, pad;
+       int len_delta, new_end, pad, payload;
        unsigned int start, end;
 
        ip6_hdr = ipv6_hdr(skb);
@@ -1346,6 +1346,8 @@ static int calipso_skbuff_setattr(struct sk_buff *skb,
        if (ret_val < 0)
                return ret_val;
 
+       ip6_hdr = ipv6_hdr(skb); /* Reset as skb_cow() may have moved it */
+
        if (len_delta) {
                if (len_delta > 0)
                        skb_push(skb, len_delta);
@@ -1355,6 +1357,8 @@ static int calipso_skbuff_setattr(struct sk_buff *skb,
                        sizeof(*ip6_hdr) + start);
                skb_reset_network_header(skb);
                ip6_hdr = ipv6_hdr(skb);
+               payload = ntohs(ip6_hdr->payload_len);
+               ip6_hdr->payload_len = htons(payload + len_delta);
        }
 
        hop = (struct ipv6_opt_hdr *)(ip6_hdr + 1);
-- 
2.9.4