netfilter: nf_tables: drop map element references from preparation phase

set .destroy callback releases the references to other objects in maps.
This is very late and it results in spurious EBUSY errors. Drop refcount
from the preparation phase instead, update set backend not to drop
reference counter from set .destroy path.

Exceptions: NFT_TRANS_PREPARE_ERROR does not require to drop the
reference counter because the transaction abort path releases the map
references for each element since the set is unbound. The abort path
also deals with releasing reference counter for new elements added to
unbound sets.

Fixes: 591054469b3e ("netfilter: nf_tables: revisit chain/object refcounting from elements")
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 18 insertions, 5 deletions

diff --git a/net/netfilter/nft_set_hash.c b/net/netfilter/nft_set_hash.c
index 76de6c8d986550..0b73cb0e752f70 100644
--- a/net/netfilter/nft_set_hash.c
+++ b/net/netfilter/nft_set_hash.c
@@ -400,19 +400,31 @@ static int nft_rhash_init(const struct nft_set *set,
 	return 0;
 }
 
+struct nft_rhash_ctx {
+	const struct nft_ctx	ctx;
+	const struct nft_set	*set;
+};
+
 static void nft_rhash_elem_destroy(void *ptr, void *arg)
 {
-	nft_set_elem_destroy(arg, ptr, true);
+	struct nft_rhash_ctx *rhash_ctx = arg;
+
+	nf_tables_set_elem_destroy(&rhash_ctx->ctx, rhash_ctx->set, ptr);
 }
 
-static void nft_rhash_destroy(const struct nft_set *set)
+static void nft_rhash_destroy(const struct nft_ctx *ctx,
+			      const struct nft_set *set)
 {
 	struct nft_rhash *priv = nft_set_priv(set);
+	struct nft_rhash_ctx rhash_ctx = {
+		.ctx	= *ctx,
+		.set	= set,
+	};
 
 	cancel_delayed_work_sync(&priv->gc_work);
 	rcu_barrier();
 	rhashtable_free_and_destroy(&priv->ht, nft_rhash_elem_destroy,
-				    (void *)set);
+				    (void *)&rhash_ctx);
 }
 
 /* Number of buckets is stored in u32, so cap our result to 1U<<31 */
@@ -643,7 +655,8 @@ static int nft_hash_init(const struct nft_set *set,
 	return 0;
 }
 
-static void nft_hash_destroy(const struct nft_set *set)
+static void nft_hash_destroy(const struct nft_ctx *ctx,
+			     const struct nft_set *set)
 {
 	struct nft_hash *priv = nft_set_priv(set);
 	struct nft_hash_elem *he;
@@ -653,7 +666,7 @@ static void nft_hash_destroy(const struct nft_set *set)
 	for (i = 0; i < priv->buckets; i++) {
 		hlist_for_each_entry_safe(he, next, &priv->table[i], node) {
 			hlist_del_rcu(&he->node);
-			nft_set_elem_destroy(set, he, true);
+			nf_tables_set_elem_destroy(ctx, set, he);
 		}
 	}
 }