netfilter: nft_set_hash: try later when GC hits EAGAIN on iteration

jira VULN-430
cve CVE-2023-4244
commit-author Pablo Neira Ayuso <[email protected]>
commit b079155

Skip GC run if iterator rewinds to the beginning with EAGAIN, otherwise GC
might collect the same element more than once.

Fixes: f6c383b ("netfilter: nf_tables: adapt set backend to use GC transaction API")
	Signed-off-by: Pablo Neira Ayuso <[email protected]>
(cherry picked from commit b079155)
	Signed-off-by: Marcin Wcisło <[email protected]>

Author: pvts-mat

net/netfilter/nft_set_hash.c

@@ -338,12 +338,9 @@ static void nft_rhash_gc(struct work_struct *work)
 
 	while ((he = rhashtable_walk_next(&hti))) {
 		if (IS_ERR(he)) {
-			if (PTR_ERR(he) != -EAGAIN) {
-				nft_trans_gc_destroy(gc);
-				gc = NULL;
-				goto try_later;
-			}
-			continue;
+			nft_trans_gc_destroy(gc);
+			gc = NULL;
+			goto try_later;
 		}
 
 		/* Ruleset has been updated, try later. */