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

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

[Liping Zhang]

From: Liping Zhang <zlpnobody@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 <zlpnobody@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

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

[Pravin Shelar]

On Sun, Jul 23, 2017 at 2:52 AM, Liping Zhang <zlpnobody@163.com> wrote:
> From: Liping Zhang <zlpnobody@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 <zlpnobody@gmail.com>

Good catch!
Acked-by: Pravin B Shelar <pshelar@ovn.org>

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

[David Miller]

From: Liping Zhang <zlpnobody@163.com>
Date: Sun, 23 Jul 2017 17:52:23 +0800

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

Applied and queued up for -stable.