netfilter: conntrack: check for NEXTHDR_NONE before header sanity checking

NEXTHDR_NONE doesn't has an IPv6 option header, so the first check
for the length will always fail and results in a confusing message
"too short" if debugging enabled. With this patch, we check for
NEXTHDR_NONE before length sanity checkings are done.

Signed-off-by: Christoph Paasch <christoph.paasch@gmail.com>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: Patrick McHardy <kaber@trash.net>

1 files changed, 4 insertions, 4 deletions

diff --git a/net/ipv6/netfilter/nf_conntrack_reasm.c b/net/ipv6/netfilter/nf_conntrack_reasm.c
index ed4d79a9e4a6..058a5e4a60c3 100644
--- a/net/ipv6/netfilter/nf_conntrack_reasm.c
+++ b/net/ipv6/netfilter/nf_conntrack_reasm.c
@@ -528,14 +528,14 @@ find_prev_fhdr(struct sk_buff *skb, u8 *prevhdrp, int *prevhoff, int *fhoff)
                 if (!ipv6_ext_hdr(nexthdr)) {
                         return -1;
                 }
-                if (len < (int)sizeof(struct ipv6_opt_hdr)) {
-                        pr_debug("too short\n");
-                        return -1;
-                }
                 if (nexthdr == NEXTHDR_NONE) {
                         pr_debug("next header is none\n");
                         return -1;
                 }
+                if (len < (int)sizeof(struct ipv6_opt_hdr)) {
+                        pr_debug("too short\n");
+                        return -1;
+                }
                 if (skb_copy_bits(skb, start, &hdr, sizeof(hdr)))
                         BUG();
                 if (nexthdr == NEXTHDR_AUTH)