linux-kernel - [Linux-kernel-mentees] [PATCH net] openvswitch: Prevent kernel-infoleak in ovs_ct_put

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Message-Id: <20200731044838.213975-1-yepeilin.cs@gmail.com>
Date:   Fri, 31 Jul 2020 00:48:38 -0400
From:   Peilin Ye <yepeilin.cs@...il.com>
To:     Pravin B Shelar <pshelar@....org>
Cc:     Peilin Ye <yepeilin.cs@...il.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Dan Carpenter <dan.carpenter@...cle.com>,
        Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel-mentees@...ts.linuxfoundation.org,
        netdev@...r.kernel.org, dev@...nvswitch.org,
        linux-kernel@...r.kernel.org
Subject: [Linux-kernel-mentees] [PATCH net] openvswitch: Prevent kernel-infoleak in ovs_ct_put_key()

ovs_ct_put_key() is potentially copying uninitialized kernel stack memory
into socket buffers, since the compiler may leave a 3-byte hole at the end
of `struct ovs_key_ct_tuple_ipv4` and `struct ovs_key_ct_tuple_ipv6`. Fix
it by initializing `orig` with memset().

Cc: stable@...r.kernel.org
Fixes: 9dd7f8907c37 ("openvswitch: Add original direction conntrack tuple to sw_flow_key.")
Suggested-by: Dan Carpenter <dan.carpenter@...cle.com>
Signed-off-by: Peilin Ye <yepeilin.cs@...il.com>
---
Reference: https://lwn.net/Articles/417989/

$ pahole -C "ovs_key_ct_tuple_ipv4" net/openvswitch/conntrack.o
struct ovs_key_ct_tuple_ipv4 {
	__be32                     ipv4_src;             /*     0     4 */
	__be32                     ipv4_dst;             /*     4     4 */
	__be16                     src_port;             /*     8     2 */
	__be16                     dst_port;             /*    10     2 */
	__u8                       ipv4_proto;           /*    12     1 */

	/* size: 16, cachelines: 1, members: 5 */
	/* padding: 3 */
	/* last cacheline: 16 bytes */
};
$ pahole -C "ovs_key_ct_tuple_ipv6" net/openvswitch/conntrack.o
struct ovs_key_ct_tuple_ipv6 {
	__be32                     ipv6_src[4];          /*     0    16 */
	__be32                     ipv6_dst[4];          /*    16    16 */
	__be16                     src_port;             /*    32     2 */
	__be16                     dst_port;             /*    34     2 */
	__u8                       ipv6_proto;           /*    36     1 */

	/* size: 40, cachelines: 1, members: 5 */
	/* padding: 3 */
	/* last cacheline: 40 bytes */
};

 net/openvswitch/conntrack.c | 38 +++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

diff --git a/net/openvswitch/conntrack.c b/net/openvswitch/conntrack.c
index 4340f25fe390..98d393e70de3 100644
--- a/net/openvswitch/conntrack.c
+++ b/net/openvswitch/conntrack.c
@@ -276,10 +276,6 @@ void ovs_ct_fill_key(const struct sk_buff *skb, struct sw_flow_key *key)
 	ovs_ct_update_key(skb, NULL, key, false, false);
 }
 
-#define IN6_ADDR_INITIALIZER(ADDR) \
-	{ (ADDR).s6_addr32[0], (ADDR).s6_addr32[1], \
-	  (ADDR).s6_addr32[2], (ADDR).s6_addr32[3] }
-
 int ovs_ct_put_key(const struct sw_flow_key *swkey,
 		   const struct sw_flow_key *output, struct sk_buff *skb)
 {
@@ -301,24 +297,30 @@ int ovs_ct_put_key(const struct sw_flow_key *swkey,
 
 	if (swkey->ct_orig_proto) {
 		if (swkey->eth.type == htons(ETH_P_IP)) {
-			struct ovs_key_ct_tuple_ipv4 orig = {
-				output->ipv4.ct_orig.src,
-				output->ipv4.ct_orig.dst,
-				output->ct.orig_tp.src,
-				output->ct.orig_tp.dst,
-				output->ct_orig_proto,
-			};
+			struct ovs_key_ct_tuple_ipv4 orig;
+
+			memset(&orig, 0, sizeof(orig));
+			orig.ipv4_src = output->ipv4.ct_orig.src;
+			orig.ipv4_dst = output->ipv4.ct_orig.dst;
+			orig.src_port = output->ct.orig_tp.src;
+			orig.dst_port = output->ct.orig_tp.dst;
+			orig.ipv4_proto = output->ct_orig_proto;
+
 			if (nla_put(skb, OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV4,
 				    sizeof(orig), &orig))
 				return -EMSGSIZE;
 		} else if (swkey->eth.type == htons(ETH_P_IPV6)) {
-			struct ovs_key_ct_tuple_ipv6 orig = {
-				IN6_ADDR_INITIALIZER(output->ipv6.ct_orig.src),
-				IN6_ADDR_INITIALIZER(output->ipv6.ct_orig.dst),
-				output->ct.orig_tp.src,
-				output->ct.orig_tp.dst,
-				output->ct_orig_proto,
-			};
+			struct ovs_key_ct_tuple_ipv6 orig;
+
+			memset(&orig, 0, sizeof(orig));
+			memcpy(orig.ipv6_src, output->ipv6.ct_orig.src.s6_addr32,
+			       sizeof(orig.ipv6_src));
+			memcpy(orig.ipv6_dst, output->ipv6.ct_orig.dst.s6_addr32,
+			       sizeof(orig.ipv6_dst));
+			orig.src_port = output->ct.orig_tp.src;
+			orig.dst_port = output->ct.orig_tp.dst;
+			orig.ipv6_proto = output->ct_orig_proto;
+
 			if (nla_put(skb, OVS_KEY_ATTR_CT_ORIG_TUPLE_IPV6,
 				    sizeof(orig), &orig))
 				return -EMSGSIZE;
-- 
2.25.1