[PATCH net] openvswitch: fix potential out of bound access in parse_ct

[Liping Zhang]

From: Liping Zhang <zlpnob...@gmail.com>

Before the 'type' is validated, we shouldn't use it to fetch the
ovs_ct_attr_lens's minlen and maxlen, else, out of bound access
may happen.

Fixes: 7f8a436eaa2c ("openvswitch: Add conntrack action")
Signed-off-by: Liping Zhang <zlpnob...@gmail.com>
---
 net/openvswitch/conntrack.c | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index e3c4c6c..03859e3 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -1310,8 +1310,8 @@ static int parse_ct(const struct nlattr *attr, struct 
ovs_conntrack_info *info,
 
        nla_for_each_nested(a, attr, rem) {
                int type = nla_type(a);
-               int maxlen = ovs_ct_attr_lens[type].maxlen;
-               int minlen = ovs_ct_attr_lens[type].minlen;
+               int maxlen;
+               int minlen;
 
                if (type > OVS_CT_ATTR_MAX) {
                        OVS_NLERR(log,
@@ -1319,6 +1319,9 @@ static int parse_ct(const struct nlattr *attr, struct 
ovs_conntrack_info *info,
                                  type, OVS_CT_ATTR_MAX);
                        return -EINVAL;
                }
+
+               maxlen = ovs_ct_attr_lens[type].maxlen;
+               minlen = ovs_ct_attr_lens[type].minlen;
                if (nla_len(a) < minlen || nla_len(a) > maxlen) {
                        OVS_NLERR(log,
                                  "Conntrack attr type has unexpected length 
(type=%d, length=%d, expected=%d)",
-- 
2.5.5