netfilter: nft_set_rbtree: allow loose matching of closing element in interval

mainline inclusion
from mainline-4.20
commit 3b18d5eba491
category: bugfix
bugzilla: 6237
CVE: NA

-------------------------------------------------

Allow to find closest matching for the right side of an interval (end
flag set on) so we allow lookups in inner ranges, eg. 10-20 in 5-25.

Fixes: ba0e4d99 ("netfilter: nf_tables: get set elements via netlink")
Reported-by: NPhil Sutter <phil@nwl.cc>
Signed-off-by: NPablo Neira Ayuso <pablo@netfilter.org>
Signed-off-by: NMao Wenan <maowenan@huawei.com>
Reviewed-by: NWei Yongjun <weiyongjun1@huawei.com>
Signed-off-by: NYang Yingliang <yangyingliang@huawei.com>

net/netfilter/nft_set_rbtree.c

@@ -135,9 +135,12 @@ static bool __nft_rbtree_get(const struct net *net, const struct nft_set *set,
 		d = memcmp(this, key, set->klen);
 		if (d < 0) {
 			parent = rcu_dereference_raw(parent->rb_left);
-			interval = rbe;
+			if (!(flags & NFT_SET_ELEM_INTERVAL_END))
+				interval = rbe;
 		} else if (d > 0) {
 			parent = rcu_dereference_raw(parent->rb_right);
+			if (flags & NFT_SET_ELEM_INTERVAL_END)
+				interval = rbe;
 		} else {
 			if (!nft_set_elem_active(&rbe->ext, genmask))
 				parent = rcu_dereference_raw(parent->rb_left);
@@ -154,7 +157,10 @@ static bool __nft_rbtree_get(const struct net *net, const struct nft_set *set,
 
 	if (set->flags & NFT_SET_INTERVAL && interval != NULL &&
 	    nft_set_elem_active(&interval->ext, genmask) &&
-	    !nft_rbtree_interval_end(interval)) {
+	    ((!nft_rbtree_interval_end(interval) &&
+	      !(flags & NFT_SET_ELEM_INTERVAL_END)) ||
+	     (nft_rbtree_interval_end(interval) &&
+	      (flags & NFT_SET_ELEM_INTERVAL_END)))) {
 		*elem = interval;
 		return true;
 	}