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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6483FC43217 for ; Fri, 6 May 2022 00:59:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1387732AbiEFBDK (ORCPT ); Thu, 5 May 2022 21:03:10 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59656 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232783AbiEFBDH (ORCPT ); Thu, 5 May 2022 21:03:07 -0400 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 818AC5EDF8; Thu, 5 May 2022 17:59:25 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 1BB04B82C77; Fri, 6 May 2022 00:59:24 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 63365C385A4; Fri, 6 May 2022 00:59:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1651798762; bh=QHLpCYQAf4+qvwVPngV5l8IrNs1LORlQXrnupp83GZw=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=a5h2RHlNwK/5saAV7Ze/fjqvxdNmdEP8Axbp3ZZz7Hb5HDtHWJBCICfECaYxNkXEK ANaNwCofZgiA1UzwJUSX+qaaSp0LS6eClnugCA0zNkRsSnX38kOKxMuzQLu9h9Aru9 61ul4/dcC/OBr5AmN74lb9td0B+IF4J82IuVNIPK2nsKrAPfVCrr4z9QwhtHrtczp2 tU8no/CqNF5wz/W4zNS+sWsHYpLVGoMGocTLtu6Tpa/HKE7L4BgiDVJ4hOXO4evxSg lfdeEuJUJMH7Tm4XyyRc7XgDnv8GxTr/iVsNxRCeJxXLe6iCxRyC+SfurDpCblt3Iv VNSJYc2ryzMfw== Date: Thu, 5 May 2022 20:08:22 -0500 From: "Gustavo A. R. Silva" To: Paul Moore Cc: Kees Cook , Steffen Klassert , Herbert Xu , "David S. Miller" , Stephen Smalley , Eric Paris , Nick Desaulniers , Xiu Jianfeng , Christian =?iso-8859-1?Q?G=F6ttsche?= , netdev@vger.kernel.org, selinux@vger.kernel.org, Alexei Starovoitov , alsa-devel@alsa-project.org, Al Viro , Andrew Gabbasov , Andrew Morton , Andy Gross , Andy Lavr , Arend van Spriel , Baowen Zheng , Bjorn Andersson , Boris Ostrovsky , Bradley Grove , brcm80211-dev-list.pdl@broadcom.com, Christian Brauner , Christian Lamparter , Chris Zankel , Cong Wang , Daniel Axtens , Daniel Vetter , Dan Williams , David Gow , David Howells , Dennis Dalessandro , devicetree@vger.kernel.org, Dexuan Cui , Dmitry Kasatkin , Eli Cohen , Eric Dumazet , Eugeniu Rosca , Felipe Balbi , Francis Laniel , Frank Rowand , Franky Lin , Greg Kroah-Hartman , Gregory Greenman , Guenter Roeck , Haiyang Zhang , Hante Meuleman , Hulk Robot , Jakub Kicinski , "James E.J. Bottomley" , James Morris , Jarkko Sakkinen , Jaroslav Kysela , Jason Gunthorpe , Jens Axboe , Johan Hedberg , Johannes Berg , Johannes Berg , John Keeping , Juergen Gross , Kalle Valo , Keith Packard , keyrings@vger.kernel.org, kunit-dev@googlegroups.com, Kuniyuki Iwashima , "K. Y. Srinivasan" , Lars-Peter Clausen , Lee Jones , Leon Romanovsky , Liam Girdwood , linux1394-devel@lists.sourceforge.net, linux-afs@lists.infradead.org, linux-arm-kernel@lists.infradead.org, linux-arm-msm@vger.kernel.org, linux-bluetooth@vger.kernel.org, linux-hardening@vger.kernel.org, linux-hyperv@vger.kernel.org, linux-integrity@vger.kernel.org, linux-rdma@vger.kernel.org, linux-scsi@vger.kernel.org, linux-security-module@vger.kernel.org, linux-usb@vger.kernel.org, linux-wireless@vger.kernel.org, linux-xtensa@linux-xtensa.org, llvm@lists.linux.dev, Loic Poulain , Louis Peens , Luca Coelho , Luiz Augusto von Dentz , Marc Dionne , Marcel Holtmann , Mark Brown , "Martin K. Petersen" , Max Filippov , Mimi Zohar , Muchun Song , Nathan Chancellor , Nuno =?iso-8859-1?Q?S=E1?= , Paolo Abeni , Rich Felker , Rob Herring , Russell King , "Serge E. Hallyn" , SHA-cyfmac-dev-list@infineon.com, Simon Horman , Stefano Stabellini , Stefan Richter , Stephen Hemminger , Tadeusz Struk , Takashi Iwai , Tom Rix , Udipto Goswami , Vincenzo Frascino , wcn36xx@lists.infradead.org, Wei Liu , xen-devel@lists.xenproject.org, Yang Yingliang Subject: Re: [PATCH 28/32] selinux: Use mem_to_flex_dup() with xfrm and sidtab Message-ID: <20220506010822.GA18891@embeddedor> References: <20220504014440.3697851-1-keescook@chromium.org> <20220504014440.3697851-29-keescook@chromium.org> <20220504234324.GA12556@embeddedor> <202205051124.6D80ABAE32@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On Thu, May 05, 2022 at 07:16:18PM -0400, Paul Moore wrote: > On Thu, May 5, 2022 at 2:39 PM Kees Cook wrote: > > On Wed, May 04, 2022 at 11:14:42PM -0400, Paul Moore wrote: > > > On Wed, May 4, 2022 at 7:34 PM Gustavo A. R. Silva > > > wrote: > > > > > > > > Hi Paul, > > > > > > > > On Wed, May 04, 2022 at 06:57:28PM -0400, Paul Moore wrote: > > > > > On Tue, May 3, 2022 at 9:57 PM Kees Cook wrote: > > > > > > > > [..] > > > > > > > > > > +++ b/include/uapi/linux/xfrm.h > > > > > > @@ -31,9 +31,9 @@ struct xfrm_id { > > > > > > struct xfrm_sec_ctx { > > > > > > __u8 ctx_doi; > > > > > > __u8 ctx_alg; > > > > > > - __u16 ctx_len; > > > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS_COUNT(__u16, ctx_len); > > > > > > __u32 ctx_sid; > > > > > > - char ctx_str[0]; > > > > > > + __DECLARE_FLEX_ARRAY_ELEMENTS(char, ctx_str); > > > > > > }; > > > > > > > > > > While I like the idea of this in principle, I'd like to hear about the > > > > > testing you've done on these patches. A previous flex array > > > > > conversion in the audit uapi headers ended up causing a problem with > > > > > > > > I'm curious about which commit caused those problems...? > > > > > > Commit ed98ea2128b6 ("audit: replace zero-length array with > > > flexible-array member"), however, as I said earlier, the problem was > > > actually with SWIG, it just happened to be triggered by the kernel > > > commit. There was a brief fedora-devel mail thread about the problem, > > > see the link below: > > > > > > * https://www.spinics.net/lists/fedora-devel/msg297991.html > > > > Wow, that's pretty weird -- it looks like SWIG was scraping the headers > > to build its conversions? I assume SWIG has been fixed now? > > I honestly don't know, the audit userspace was hacking around it with > some header file duplication/munging last I heard, but I try to avoid > having to touch Steve's audit userspace code. > > > > To reiterate, I'm supportive of changes like this, but I would like to > > > hear how it was tested to ensure there are no unexpected problems with > > > userspace. If there are userspace problems it doesn't mean we can't > > > make changes like this, it just means we need to ensure that the > > > userspace issues are resolved first. > > > > Well, as this is the first and only report of any problems with [0] -> [] > > conversions (in UAPI or anywhere) that I remember seeing, and they've > > been underway since at least v5.9, I hadn't been doing any new testing. > > ... and for whatever it is worth, I wasn't expecting it to be a > problem either. Surprise :) > > > So, for this case, I guess I should ask what tests you think would be > > meaningful here? Anything using #include should be fine: > > https://codesearch.debian.net/search?q=linux%2Fxfrm.h&literal=1&perpkg=1 > > Which leaves just this, which may be doing something weird: > > > > libabigail_2.0-1/tests/data/test-diff-filter/test-PR27569-v0.abi > > > > > > > > > > > > > > But I see that SWIG doesn't show up in a search for linux/audit.h: > > https://codesearch.debian.net/search?q=linux%2Faudit.h&literal=1&perpkg=1 > > > > So this may not be a sufficient analysis... > > I think from a practical perspective ensuring that the major IPsec/IKE > tools, e.g. the various *SWANs, that know about labeled IPSec still > build and can set/get the SA/SPD labels correctly would be sufficient. > I seriously doubt there would be any problems, but who knows. There are certainly some cases in which the transformation of zero-length arrays into flexible-array members can bring some issues to the surface[1][2]. This is the first time that we know of one of them in user-space. However, we haven't transformed the arrays in UAPI yet (with the exception of a couple of cases[3][4]). But that is something that we are planning to try soon[5]. -- Gustavo [1] https://github.com/KSPP/linux/issues?q=invalid+use+of+flexible+array [2] https://github.com/KSPP/linux/issues?q=invalid+application+of+%E2%80%98sizeof%E2%80%99+to+incomplete+type [3] https://git.kernel.org/linus/db243b796439c0caba47865564d8acd18a301d18 [4] https://git.kernel.org/linus/d6cdad870358128c1e753e6258e295ab8a5a2429 [5] https://git.kernel.org/pub/scm/linux/kernel/git/gustavoars/linux.git/commit/?h=for-next/kspp-fam0-uapi