From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4CCDAC35280 for ; Fri, 1 May 2020 20:30:18 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 256BA2166E for ; Fri, 1 May 2020 20:30:18 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726307AbgEAUaS (ORCPT ); Fri, 1 May 2020 16:30:18 -0400 Received: from correo.us.es ([193.147.175.20]:33702 "EHLO mail.us.es" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726045AbgEAUaR (ORCPT ); Fri, 1 May 2020 16:30:17 -0400 Received: from antivirus1-rhel7.int (unknown [192.168.2.11]) by mail.us.es (Postfix) with ESMTP id D0B8518CDC0 for ; Fri, 1 May 2020 22:30:15 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id BF3BA6D28C for ; Fri, 1 May 2020 22:30:15 +0200 (CEST) Received: by antivirus1-rhel7.int (Postfix, from userid 99) id BD5412067E; Fri, 1 May 2020 22:30:15 +0200 (CEST) Received: from antivirus1-rhel7.int (localhost [127.0.0.1]) by antivirus1-rhel7.int (Postfix) with ESMTP id BE6F1BAABF; Fri, 1 May 2020 22:30:13 +0200 (CEST) Received: from 192.168.1.97 (192.168.1.97) by antivirus1-rhel7.int (F-Secure/fsigk_smtp/550/antivirus1-rhel7.int); Fri, 01 May 2020 22:30:13 +0200 (CEST) X-Virus-Status: clean(F-Secure/fsigk_smtp/550/antivirus1-rhel7.int) Received: from us.es (unknown [90.77.255.23]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) (Authenticated sender: 1984lsi) by entrada.int (Postfix) with ESMTPSA id 9EEC54301DE0; Fri, 1 May 2020 22:30:13 +0200 (CEST) Date: Fri, 1 May 2020 22:30:13 +0200 X-SMTPAUTHUS: auth mail.us.es From: Pablo Neira Ayuso To: michael-dev Cc: netfilter-devel@vger.kernel.org Subject: Re: [PATCH 3/3] datatype: fix double-free resulting in use-after-free in datatype_free Message-ID: <20200501203013.GA29652@salvia> References: <20200501154819.2984-1-michael-dev@fami-braun.de> <20200501154819.2984-3-michael-dev@fami-braun.de> <20200501192703.GC13722@salvia> <545922fa020689faa17dae656320fe58@fami-braun.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <545922fa020689faa17dae656320fe58@fami-braun.de> User-Agent: Mutt/1.10.1 (2018-07-13) X-Virus-Scanned: ClamAV using ClamSMTP Sender: netfilter-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netfilter-devel@vger.kernel.org On Fri, May 01, 2020 at 09:59:35PM +0200, michael-dev wrote: > Am 01.05.2020 21:27, schrieb Pablo Neira Ayuso: > > On Fri, May 01, 2020 at 05:48:18PM +0200, Michael Braun wrote: > > > + if (dtype == expr->dtype) > > > + return; // do not free dtype before incrementing refcnt again > > > > The problem you describe (use-after-free) happens in this case, right? > > The problem is more likely due to concat_expr_parse_udata not calling > datatype_get, > because otherwise datatype_get would be in the backtrace of ASAN. > > > > > datatype_set(expr, expr->dtype); > > > > Or am I missing anything? > > But while debugging the above output, I added assert(dtype != expr->dtype) > here > and that crashed. So I'm sure something like this is happening. Right. # nft add rule ip x y ct state new,established,related,untracked # nft list ruleset nft: datatype.c:1086: datatype_set: Assertion `expr->dtype != dtype' failed. Aborted > And the whole thing was nasty to debug, so I added this one just be sure it > does not happen again. > > As ASAN should hit on datatype_get incrementing refcnt if datatype_free had > actually freed it, > assert was probaby not seeing an DTYPE_F_ALLOC instance. > But I dig not deeper here, as I felt this return is safe to add. I'm going to apply this. I think it's safe to turn this into noop.