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

[ Upstream commit e331473 ]

Similarly to what has been done in 8b4c3cd ("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: 5bc1701 ("net: sched: introduce multichain support for filters")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

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);
 
@@ -559,7 +561,7 @@ static int tc_ctl_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;
 
@@ -836,7 +838,8 @@ static int tc_dump_tfilter(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;