netfilter: nf_tables: fix unexpected EOPNOTSUPP error

If the object type doesn't implement an update operation and the user tries to
update it will silently ignore the update operation.

Fixes: aa4095a156 ("netfilter: nf_tables: fix possible null-pointer dereference in object update")
Signed-off-by: Fernando Fernandez Mancera <ffmancera@riseup.net>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -5143,9 +5143,6 @@ static int nf_tables_updobj(const struct nft_ctx *ctx,
 	struct nft_trans *trans;
 	int err;
 
-	if (!obj->ops->update)
-		return -EOPNOTSUPP;
-
 	trans = nft_trans_alloc(ctx, NFT_MSG_NEWOBJ,
 				sizeof(struct nft_trans_obj));
 	if (!trans)
@@ -6499,7 +6496,8 @@ static void nft_obj_commit_update(struct nft_trans *trans)
 	obj = nft_trans_obj(trans);
 	newobj = nft_trans_obj_newobj(trans);
 
-	obj->ops->update(obj, newobj);
+	if (obj->ops->update)
+		obj->ops->update(obj, newobj);
 
 	kfree(newobj);
 }