netfilter: nf_tables: bogus EBUSY when deleting set after flush

Set deletion after flush coming in the same batch results in EBUSY. Add
set use counter to track the number of references to this set from
rules. We cannot rely on the list of bindings for this since such list
is still populated from the preparation phase.

Reported-by: Václav Zindulka <vaclav.zindulka@tlapnet.cz>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 27 insertions, 1 deletions

diff --git a/net/netfilter/nf_tables_api.c b/net/netfilter/nf_tables_api.c
index 1333bf97dc26..ca09ef037ca5 100644
--- a/net/netfilter/nf_tables_api.c
+++ b/net/netfilter/nf_tables_api.c
@@ -3672,6 +3672,9 @@ err1:
 
 static void nft_set_destroy(struct nft_set *set)
 {
+	if (WARN_ON(set->use > 0))
+		return;
+
 	set->ops->destroy(set);
 	module_put(to_set_type(set->ops)->owner);
 	kfree(set->name);
@@ -3712,7 +3715,7 @@ static int nf_tables_delset(struct net *net, struct sock *nlsk,
 		NL_SET_BAD_ATTR(extack, attr);
 		return PTR_ERR(set);
 	}
-	if (!list_empty(&set->bindings) ||
+	if (set->use ||
 	    (nlh->nlmsg_flags & NLM_F_NONREC && atomic_read(&set->nelems) > 0)) {
 		NL_SET_BAD_ATTR(extack, attr);
 		return -EBUSY;
@@ -3742,6 +3745,9 @@ int nf_tables_bind_set(const struct nft_ctx *ctx, struct nft_set *set,
 	struct nft_set_binding *i;
 	struct nft_set_iter iter;
 
+	if (set->use == UINT_MAX)
+		return -EOVERFLOW;
+
 	if (!list_empty(&set->bindings) && nft_set_is_anonymous(set))
 		return -EBUSY;
 
@@ -3769,6 +3775,7 @@ bind:
 	binding->chain = ctx->chain;
 	list_add_tail_rcu(&binding->list, &set->bindings);
 	nft_set_trans_bind(ctx, set);
+	set->use++;
 
 	return 0;
 }
@@ -3788,6 +3795,25 @@ void nf_tables_unbind_set(const struct nft_ctx *ctx, struct nft_set *set,
 }
 EXPORT_SYMBOL_GPL(nf_tables_unbind_set);
 
+void nf_tables_deactivate_set(const struct nft_ctx *ctx, struct nft_set *set,
+			      struct nft_set_binding *binding,
+			      enum nft_trans_phase phase)
+{
+	switch (phase) {
+	case NFT_TRANS_PREPARE:
+		set->use--;
+		return;
+	case NFT_TRANS_ABORT:
+	case NFT_TRANS_RELEASE:
+		set->use--;
+		/* fall through */
+	default:
+		nf_tables_unbind_set(ctx, set, binding,
+				     phase == NFT_TRANS_COMMIT);
+	}
+}
+EXPORT_SYMBOL_GPL(nf_tables_deactivate_set);
+
 void nf_tables_destroy_set(const struct nft_ctx *ctx, struct nft_set *set)
 {
 	if (list_empty(&set->bindings) && nft_set_is_anonymous(set))