netfilter: nft_set_rbtree: skip sync GC for new elements in this transaction

jira VULN-158866
cve CVE-2023-52433
commit-author Pablo Neira Ayuso <[email protected]>
commit 2ee52ae

New elements in this transaction might expired before such transaction
ends. Skip sync GC for such elements otherwise commit path might walk
over an already released object. Once transaction is finished, async GC
will collect such expired element.

Fixes: f6c383b ("netfilter: nf_tables: adapt set backend to use GC transaction API")
	Signed-off-by: Pablo Neira Ayuso <[email protected]>
	Signed-off-by: Florian Westphal <[email protected]>
(cherry picked from commit 2ee52ae)
	Signed-off-by: Marcin Wcisło <[email protected]>

Author: pvts-mat

net/netfilter/nft_set_rbtree.c

@@ -312,6 +312,7 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
 	struct nft_rbtree_elem *rbe, *rbe_le = NULL, *rbe_ge = NULL;
 	struct rb_node *node, *next, *parent, **p, *first = NULL;
 	struct nft_rbtree *priv = nft_set_priv(set);
+	u8 cur_genmask = nft_genmask_cur(net);
 	u8 genmask = nft_genmask_next(net);
 	int d, err;
 
@@ -357,8 +358,11 @@ static int __nft_rbtree_insert(const struct net *net, const struct nft_set *set,
 		if (!nft_set_elem_active(&rbe->ext, genmask))
 			continue;
 
-		/* perform garbage collection to avoid bogus overlap reports. */
-		if (nft_set_elem_expired(&rbe->ext)) {
+		/* perform garbage collection to avoid bogus overlap reports
+		 * but skip new elements in this transaction.
+		 */
+		if (nft_set_elem_expired(&rbe->ext) &&
+		    nft_set_elem_active(&rbe->ext, cur_genmask)) {
 			err = nft_rbtree_gc_elem(set, priv, rbe, genmask);
 			if (err < 0)
 				return err;