netfilter: nf_tables: GC transaction race with abort path

jira VULN-597
subsystem-sync netfilter:nf_tables 4.18.0-534
commit-author Pablo Neira Ayuso <pablo@netfilter.org>
commit 7203443
upstream-diff Some minor differences due to pernet goo - not important.

Abort path is missing a synchronization point with GC transactions. Add
GC sequence number hence any GC transaction losing race will be
discarded.

Fixes: 5f68718 ("netfilter: nf_tables: GC transaction API to avoid race with control plane")
	Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
	Signed-off-by: Florian Westphal <fw@strlen.de>
(cherry-picked from commit 7203443)
	Signed-off-by: Greg Rose <g.v.rose@ciq.com>

Author: gvrose8192

net/netfilter/nf_tables_api.c

@@ -8601,6 +8601,12 @@ static int nf_tables_abort(struct net *net, struct sk_buff *skb,
 			   enum nfnl_abort_action action)
 {
 	struct nftables_pernet *nft_net = nft_pernet(net);
+	unsigned int gc_seq;
+	int ret;
+
+	gc_seq = nft_gc_seq_begin(nft_net);
+	ret = __nf_tables_abort(net, action);
+	nft_gc_seq_end(nft_net, gc_seq);
 
 	mutex_unlock(&net->nft_commit_mutex);