netfilter: nf_tables: hook list memleak in flowtable deletion

After looking up for the flowtable hooks that need to be removed,
release the hook objects in the deletion list. The error path needs to
released these hook objects too.

Fixes: abadb2f8 ("netfilter: nf_tables: delete devices from flowtable")
Reported-by: syzbot+eb9d5924c51d6d59e094@syzkaller.appspotmail.com
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

net/netfilter/nf_tables_api.c

@@ -6550,12 +6550,22 @@ static int nf_tables_newflowtable(struct net *net, struct sock *nlsk,
 	return err;
 }
 
+static void nft_flowtable_hook_release(struct nft_flowtable_hook *flowtable_hook)
+{
+	struct nft_hook *this, *next;
+
+	list_for_each_entry_safe(this, next, &flowtable_hook->list, list) {
+		list_del(&this->list);
+		kfree(this);
+	}
+}
+
 static int nft_delflowtable_hook(struct nft_ctx *ctx,
 				 struct nft_flowtable *flowtable)
 {
 	const struct nlattr * const *nla = ctx->nla;
 	struct nft_flowtable_hook flowtable_hook;
-	struct nft_hook *this, *next, *hook;
+	struct nft_hook *this, *hook;
 	struct nft_trans *trans;
 	int err;
 
@@ -6564,33 +6574,40 @@ static int nft_delflowtable_hook(struct nft_ctx *ctx,
 	if (err < 0)
 		return err;
 
-	list_for_each_entry_safe(this, next, &flowtable_hook.list, list) {
+	list_for_each_entry(this, &flowtable_hook.list, list) {
 		hook = nft_hook_list_find(&flowtable->hook_list, this);
 		if (!hook) {
 			err = -ENOENT;
 			goto err_flowtable_del_hook;
 		}
 		hook->inactive = true;
-		list_del(&this->list);
-		kfree(this);
 	}
 
 	trans = nft_trans_alloc(ctx, NFT_MSG_DELFLOWTABLE,
 				sizeof(struct nft_trans_flowtable));
-	if (!trans)
-		return -ENOMEM;
+	if (!trans) {
+		err = -ENOMEM;
+		goto err_flowtable_del_hook;
+	}
 
 	nft_trans_flowtable(trans) = flowtable;
 	nft_trans_flowtable_update(trans) = true;
 	INIT_LIST_HEAD(&nft_trans_flowtable_hooks(trans));
+	nft_flowtable_hook_release(&flowtable_hook);
 
 	list_add_tail(&trans->list, &ctx->net->nft.commit_list);
 
 	return 0;
 
 err_flowtable_del_hook:
-	list_for_each_entry(hook, &flowtable_hook.list, list)
+	list_for_each_entry(this, &flowtable_hook.list, list) {
+		hook = nft_hook_list_find(&flowtable->hook_list, this);
+		if (!hook)
+			break;
+
 		hook->inactive = false;
+	}
+	nft_flowtable_hook_release(&flowtable_hook);
 
 	return err;
 }