From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from lindbergh.monkeyblade.net (lindbergh.monkeyblade.net [23.128.96.19])
	(using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits))
	(No client certificate requested)
	by smtp.subspace.kernel.org (Postfix) with ESMTPS id C39D4D53F
	for <netdev@vger.kernel.org>; Wed, 21 Jun 2023 10:46:19 +0000 (UTC)
Received: from Chamillionaire.breakpoint.cc (Chamillionaire.breakpoint.cc [IPv6:2a0a:51c0:0:237:300::1])
	by lindbergh.monkeyblade.net (Postfix) with ESMTPS id B26281BDF;
	Wed, 21 Jun 2023 03:46:14 -0700 (PDT)
Received: from fw by Chamillionaire.breakpoint.cc with local (Exim 4.92)
	(envelope-from <fw@strlen.de>)
	id 1qBvLf-0006WT-QB; Wed, 21 Jun 2023 12:46:03 +0200
Date: Wed, 21 Jun 2023 12:46:03 +0200
From: Florian Westphal <fw@strlen.de>
To: "Igor A. Artemiev" <Igor.A.Artemiev@mcst.ru>
Cc: Florian Westphal <fw@strlen.de>,
	Pablo Neira Ayuso <pablo@netfilter.org>,
	Jozsef Kadlecsik <kadlec@netfilter.org>,
	"David S . Miller" <davem@davemloft.net>,
	Paolo Abeni <pabeni@redhat.com>, Jakub Kicinski <kuba@kernel.org>,
	netfilter-devel@vger.kernel.org, coreteam@netfilter.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	lvc-project@linuxtesting.org
Subject: Re: [lvc-project] [PATCH] netfilter: ebtables: remove unnecessary
 NULL check
Message-ID: <20230621104603.GA24035@breakpoint.cc>
References: <20230620152549.2109063-1-Igor.A.Artemiev@mcst.ru>
 <20230620163806.GB3799@breakpoint.cc>
 <f687fe6f-3330-a9c5-4760-f753638c7b03@mcst.ru>
Precedence: bulk
X-Mailing-List: netdev@vger.kernel.org
List-Id: <netdev.vger.kernel.org>
List-Subscribe: <mailto:netdev+subscribe@vger.kernel.org>
List-Unsubscribe: <mailto:netdev+unsubscribe@vger.kernel.org>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <f687fe6f-3330-a9c5-4760-f753638c7b03@mcst.ru>
User-Agent: Mutt/1.10.1 (2018-07-13)
X-Spam-Status: No, score=-4.2 required=5.0 tests=BAYES_00,RCVD_IN_DNSWL_MED,
	SPF_HELO_PASS,SPF_PASS,T_SCC_BODY_TEXT_LINE autolearn=ham
	autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
	lindbergh.monkeyblade.net

Igor A. Artemiev <Igor.A.Artemiev@mcst.ru> wrote:
> On 6/20/23 19:38, Florian Westphal wrote:
> > Igor Artemiev <Igor.A.Artemiev@mcst.ru> wrote:
> > > In ebt_do_table() 'private->chainstack' cannot be NULL
> > > and the 'cs' pointer is dereferenced below, so it does not make
> > > sense to compare 'private->chainstack' with NULL.
> > ?  Why do you think that?
> > 
> The 'cs' pointer is dereferenced below without checking, as it is assumed to
> always be initialized with 'private->chainstack[smp_processor_id()]'.

No, its not.  The dereferencing is conditional, as is the allocation
of the chainstack.

No user defined chains, no chain stack.

With this change, "ebtables-legacy -A INPUT" causes kernel panic.