Linux Ethernet Bridging - Feb 2017 - [Bridge] [PATCH net-next] bridge: tunnel: fix attribute checks in br_parse_vlan_tunnel_info

On 07/02/17 12:25, Colin Ian King wrote:
> Hi,
> 
> Static analysis with CoverityScan on net/bridge/br_netlink_tunnel.c has
> picked up and issue where tb[] is being referenced but contains
> uninitialized data.
> 
> 222 int br_parse_vlan_tunnel_info(struct nlattr *attr,
> 223                               struct vtunnel_info *tinfo)
> 224 {
> 
>     1. var_decl: Declaring variable tb without initializer.
> 
> 225         struct nlattr *tb[IFLA_BRIDGE_VLAN_TUNNEL_MAX + 1];
> 226         u32 tun_id;
> 227         u16 vid, flags = 0;
> 228         int err;
> 229
> 230         memset(tinfo, 0, sizeof(*tinfo));
> 231
> 
>     CID 1400055 (#1 of 1): Uninitialized pointer read (UNINIT)2.
> uninit_use: Using uninitialized value tb[IFLA_BRIDGE_VLAN_TUNNEL_ID].
> 
> 232         if (!tb[IFLA_BRIDGE_VLAN_TUNNEL_ID] ||
> 233             !tb[IFLA_BRIDGE_VLAN_TUNNEL_VID])
> 234                 return -EINVAL;
> 
> Colin
> 
Good catch, these should go after the parsing.

These checks should go after the attributes have been parsed otherwise
we're using tb uninitialized.

Fixes: efa5356b0d97 ("bridge: per vlan dst_metadata netlink support")
Reported-by: Colin Ian King <colin.king at canonical.com>
Signed-off-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
---
 net/bridge/br_netlink_tunnel.c | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/net/bridge/br_netlink_tunnel.c b/net/bridge/br_netlink_tunnel.c
index 99c68012c9d4..62eaf750bd9e 100644
--- a/net/bridge/br_netlink_tunnel.c
+++ b/net/bridge/br_netlink_tunnel.c
@@ -229,15 +229,15 @@ int br_parse_vlan_tunnel_info(struct nlattr *attr,
 
 	memset(tinfo, 0, sizeof(*tinfo));
 
-	if (!tb[IFLA_BRIDGE_VLAN_TUNNEL_ID] ||
-	    !tb[IFLA_BRIDGE_VLAN_TUNNEL_VID])
-		return -EINVAL;
-
 	err = nla_parse_nested(tb, IFLA_BRIDGE_VLAN_TUNNEL_MAX,
 			       attr, vlan_tunnel_policy);
 	if (err < 0)
 		return err;
 
+	if (!tb[IFLA_BRIDGE_VLAN_TUNNEL_ID] ||
+	    !tb[IFLA_BRIDGE_VLAN_TUNNEL_VID])
+		return -EINVAL;
+
 	tun_id = nla_get_u32(tb[IFLA_BRIDGE_VLAN_TUNNEL_ID]);
 	vid = nla_get_u16(tb[IFLA_BRIDGE_VLAN_TUNNEL_VID]);
 	if (vid >= VLAN_VID_MASK)
-- 
2.1.4