[PATCH 4.12 075/106] openvswitch: fix potential out of bound access in parse_ct

[Greg Kroah-Hartman]

4.12-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Liping Zhang <zlpnobody@xxxxxxxxx>


[ Upstream commit 69ec932e364b1ba9c3a2085fe96b76c8a3f71e7c ]

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 <zlpnobody@xxxxxxxxx>
Acked-by: Pravin B Shelar <pshelar@xxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
 net/openvswitch/conntrack.c |    7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -1289,8 +1289,8 @@ static int parse_ct(const struct nlattr
 
 	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,
@@ -1298,6 +1298,9 @@ static int parse_ct(const struct nlattr
 				  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)",