net: sched: Add policy validation for tc attributes

A number of TC attributes are processed without proper validation
(e.g., length checks). Add a tca policy for all input attributes and use
when invoking nlmsg_parse.

The 2 Fixes tags below cover the latest additions. The other attributes
are a string (KIND), nested attribute (OPTIONS which does seem to have
validation in most cases), for dumps only or a flag.

Fixes: 5bc1701 ("net: sched: introduce multichain support for filters")
Fixes: d47a6b0 ("net: sched: introduce ingress/egress block index attributes for qdisc")
Signed-off-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_api.c

@@ -1311,6 +1311,18 @@ check_loop_fn(struct Qdisc *q, unsigned long cl, struct qdisc_walker *w)
  * Delete/get qdisc.
  */
 
+const struct nla_policy rtm_tca_policy[TCA_MAX + 1] = {
+	[TCA_KIND]		= { .type = NLA_STRING },
+	[TCA_OPTIONS]		= { .type = NLA_NESTED },
+	[TCA_RATE]		= { .type = NLA_BINARY,
+				    .len = sizeof(struct tc_estimator) },
+	[TCA_STAB]		= { .type = NLA_NESTED },
+	[TCA_DUMP_INVISIBLE]	= { .type = NLA_FLAG },
+	[TCA_CHAIN]		= { .type = NLA_U32 },
+	[TCA_INGRESS_BLOCK]	= { .type = NLA_U32 },
+	[TCA_EGRESS_BLOCK]	= { .type = NLA_U32 },
+};
+
 static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 			struct netlink_ext_ack *extack)
 {
@@ -1327,7 +1339,8 @@ static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 	    !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
-	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, rtm_tca_policy,
+			  extack);
 	if (err < 0)
 		return err;
 
@@ -1411,7 +1424,8 @@ static int tc_modify_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 
 replay:
 	/* Reinit, just in case something touches this. */
-	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, rtm_tca_policy,
+			  extack);
 	if (err < 0)
 		return err;
 
@@ -1645,7 +1659,8 @@ static int tc_dump_qdisc(struct sk_buff *skb, struct netlink_callback *cb)
 	idx = 0;
 	ASSERT_RTNL();
 
-	err = nlmsg_parse(nlh, sizeof(struct tcmsg), tca, TCA_MAX, NULL, NULL);
+	err = nlmsg_parse(nlh, sizeof(struct tcmsg), tca, TCA_MAX,
+			  rtm_tca_policy, NULL);
 	if (err < 0)
 		return err;
 
@@ -1864,7 +1879,8 @@ static int tc_ctl_tclass(struct sk_buff *skb, struct nlmsghdr *n,
 	    !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
-	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*tcm), tca, TCA_MAX, rtm_tca_policy,
+			  extack);
 	if (err < 0)
 		return err;