net/sched: cls_api: add missing validation of netlink attributes

Similarly to what has been done in 8b4c3cdd9d ("net: sched: Add policy
validation for tc attributes"), fix classifier code to add validation of
TCA_CHAIN and TCA_KIND netlink attributes.

tested with:
 # ./tdc.py -c filter

v2: Let sch_api and cls_api share nla_policy they have in common, thanks
    to David Ahern.
v3: Avoid EXPORT_SYMBOL(), as validation of those attributes is not done
    by TC modules, thanks to Cong Wang.
    While at it, restore the 'Delete / get qdisc' comment to its orginal
    position, just above tc_get_qdisc() function prototype.

Fixes: 5bc1701881 ("net: sched: introduce multichain support for filters")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_api.c

@@ -31,6 +31,8 @@
 #include <net/pkt_sched.h>
 #include <net/pkt_cls.h>
 
+extern const struct nla_policy rtm_tca_policy[TCA_MAX + 1];
+
 /* The list of all installed classifier types */
 static LIST_HEAD(tcf_proto_base);
 
@@ -1211,7 +1213,7 @@ static int tc_new_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 replay:
 	tp_created = 0;
 
-	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, rtm_tca_policy, extack);
 	if (err < 0)
 		return err;
 
@@ -1360,7 +1362,7 @@ static int tc_del_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	if (!netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
-	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, rtm_tca_policy, extack);
 	if (err < 0)
 		return err;
 
@@ -1475,7 +1477,7 @@ static int tc_get_tfilter(struct sk_buff *skb, struct nlmsghdr *n,
 	void *fh = NULL;
 	int err;
 
-	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, rtm_tca_policy, extack);
 	if (err < 0)
 		return err;
 
@@ -1838,7 +1840,7 @@ static int tc_ctl_chain(struct sk_buff *skb, struct nlmsghdr *n,
 		return -EPERM;
 
 replay:
-	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, NULL, extack);
+	err = nlmsg_parse(n, sizeof(*t), tca, TCA_MAX, rtm_tca_policy, extack);
 	if (err < 0)
 		return err;
 
@@ -1949,7 +1951,8 @@ static int tc_dump_chain(struct sk_buff *skb, struct netlink_callback *cb)
 	if (nlmsg_len(cb->nlh) < sizeof(*tcm))
 		return skb->len;
 
-	err = nlmsg_parse(cb->nlh, sizeof(*tcm), tca, TCA_MAX, NULL, NULL);
+	err = nlmsg_parse(cb->nlh, sizeof(*tcm), tca, TCA_MAX, rtm_tca_policy,
+			  NULL);
 	if (err)
 		return err;
 

net/sched/sch_api.c

@@ -1307,10 +1307,6 @@ check_loop_fn(struct Qdisc *q, unsigned long cl, struct qdisc_walker *w)
 	return 0;
 }
 
-/*
- * Delete/get qdisc.
- */
-
 const struct nla_policy rtm_tca_policy[TCA_MAX + 1] = {
 	[TCA_KIND]		= { .type = NLA_STRING },
 	[TCA_OPTIONS]		= { .type = NLA_NESTED },
@@ -1323,6 +1319,10 @@ const struct nla_policy rtm_tca_policy[TCA_MAX + 1] = {
 	[TCA_EGRESS_BLOCK]	= { .type = NLA_U32 },
 };
 
+/*
+ * Delete/get qdisc.
+ */
+
 static int tc_get_qdisc(struct sk_buff *skb, struct nlmsghdr *n,
 			struct netlink_ext_ack *extack)
 {