[NETFILTER]: {ip, nf}_conntrack_sctp: fix remotely triggerable NULL ptr dereference (CVE-2007-2876)

When creating a new connection by sending an unknown chunk type, we
don't transition to a valid state, causing a NULL pointer dereference
in sctp_packet when accessing sctp_timeouts[SCTP_CONNTRACK_NONE].

Fix by don't creating new conntrack entry if initial state is invalid.

Noticed by Vilmos Nebehaj <vilmos.nebehaj@ramsys.hu>

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>
Signed-off-by: Chris Wright <chrisw@sous-sol.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/netfilter/nf_conntrack_proto_sctp.c b/net/netfilter/nf_conntrack_proto_sctp.c
index 265769e5002b..debfe61378a1 100644
--- a/net/netfilter/nf_conntrack_proto_sctp.c
+++ b/net/netfilter/nf_conntrack_proto_sctp.c
@@ -431,7 +431,8 @@ static int sctp_new(struct nf_conn *conntrack, const struct sk_buff *skb,
                                          SCTP_CONNTRACK_NONE, sch->type);
 
                 /* Invalid: delete conntrack */
-                if (newconntrack == SCTP_CONNTRACK_MAX) {
+                if (newconntrack == SCTP_CONNTRACK_NONE ||
+                    newconntrack == SCTP_CONNTRACK_MAX) {
                         pr_debug("nf_conntrack_sctp: invalid new deleting.\n");
                         return 0;
                 }