net/sched: matchall: add missing validation of TCA_MATCHALL_FLAGS

unlike other classifiers that can be offloaded (i.e. users can set flags
like 'skip_hw' and 'skip_sw'), 'cls_matchall' doesn't validate the size
of netlink attribute 'TCA_MATCHALL_FLAGS' provided by user: add a proper
entry to mall_policy.

Fixes: b87f793 ("net/sched: Add match-all classifier hw offloading.")
Signed-off-by: Davide Caratti <dcaratti@redhat.com>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/cls_matchall.c

@@ -157,6 +157,7 @@ static void *mall_get(struct tcf_proto *tp, u32 handle)
 static const struct nla_policy mall_policy[TCA_MATCHALL_MAX + 1] = {
 	[TCA_MATCHALL_UNSPEC]		= { .type = NLA_UNSPEC },
 	[TCA_MATCHALL_CLASSID]		= { .type = NLA_U32 },
+	[TCA_MATCHALL_FLAGS]		= { .type = NLA_U32 },
 };
 
 static int mall_set_parms(struct net *net, struct tcf_proto *tp,