bridge: Sanitize IFLA_EXT_MASK for AF_BRIDGE:RTM_GETLINK

Only search for IFLA_EXT_MASK if the message actually carries a
ifinfomsg header and validate minimal length requirements for
IFLA_EXT_MASK.

Fixes: 6cbdceeb ("bridge: Dump vlan information from a bridge port")
Cc: Vlad Yasevich <vyasevic@redhat.com>
Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 12 insertions, 5 deletions

diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index 5a853f8fad6c..b9b7dfaf202b 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -2685,13 +2685,20 @@ static int rtnl_bridge_getlink(struct sk_buff *skb, struct netlink_callback *cb)
         int idx = 0;
         u32 portid = NETLINK_CB(cb->skb).portid;
         u32 seq = cb->nlh->nlmsg_seq;
-        struct nlattr *extfilt;
         u32 filter_mask = 0;
 
-        extfilt = nlmsg_find_attr(cb->nlh, sizeof(struct ifinfomsg),
-                                  IFLA_EXT_MASK);
-        if (extfilt)
-                filter_mask = nla_get_u32(extfilt);
+        if (nlmsg_len(cb->nlh) > sizeof(struct ifinfomsg)) {
+                struct nlattr *extfilt;
+
+                extfilt = nlmsg_find_attr(cb->nlh, sizeof(struct ifinfomsg),
+                                          IFLA_EXT_MASK);
+                if (extfilt) {
+                        if (nla_len(extfilt) < sizeof(filter_mask))
+                                return -EINVAL;
+
+                        filter_mask = nla_get_u32(extfilt);
+                }
+        }
 
         rcu_read_lock();
         for_each_netdev_rcu(net, dev) {