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=-7.1 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=ham 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 66D08C35242 for ; Tue, 11 Feb 2020 20:27:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3641B20714 for ; Tue, 11 Feb 2020 20:27:46 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=embeddedor.com header.i=@embeddedor.com header.b="lMUWu+8n" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731132AbgBKU1p (ORCPT ); Tue, 11 Feb 2020 15:27:45 -0500 Received: from gateway33.websitewelcome.com ([192.185.145.23]:48491 "EHLO gateway33.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727910AbgBKU1o (ORCPT ); Tue, 11 Feb 2020 15:27:44 -0500 Received: from cm11.websitewelcome.com (cm11.websitewelcome.com [100.42.49.5]) by gateway33.websitewelcome.com (Postfix) with ESMTP id 8FE50133785 for ; Tue, 11 Feb 2020 14:27:43 -0600 (CST) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id 1c8FjDiCsSl8q1c8FjwpN9; Tue, 11 Feb 2020 14:27:43 -0600 X-Authority-Reason: nr=8 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=embeddedor.com; s=default; h=Content-Transfer-Encoding:Content-Type: In-Reply-To:MIME-Version:Date:Message-ID:From:References:Cc:To:Subject:Sender :Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id:List-Help: List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=PPWWdaifeZzk9RLwFlJ5meY5m2rkkfSdPZkRBHo2zLg=; b=lMUWu+8neDtCWoM7HC7ndnZLve CNLfWODYRH0dKfbYGWeisHnLSxwNAv69i74ZGjwscfb0/qmOAypEZD+6HBJFL+fTIjsho7HOEtwG1 MkHOsPZmKwA2Q5pvtdb3Fiw15YCeLaJIrWEpEr+djGYU1UyM4rUwYKd2T+uOu6kMzs+8Zoi0P1/fV bYOr6VWSaXgDAjg9G1QXzRO17lr07NmB7n60KgWN3y8bbtk63wqdlYlBwoJS8OYKCJNFDxDDjsT2Q kEdxfEnZv6oclhIyZH55YS7WheIc/5xVs6zTjk/g7Dp8gA06Fof0OK0Aw9jCl+XbJ8x4i5IDqZi6S pym9IHiw==; Received: from [200.68.140.36] (port=27441 helo=[192.168.43.131]) by gator4166.hostgator.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES128-GCM-SHA256:128) (Exim 4.92) (envelope-from ) id 1j1c8F-001jRM-5K; Tue, 11 Feb 2020 14:27:43 -0600 Subject: Re: [PATCH] treewide: Replace zero-length arrays with flexible-array member To: Kees Cook Cc: Greg KH , linux-kernel@vger.kernel.org, "David S. Miller" , linux-crypto@vger.kernel.org, netdev@vger.kernel.org, linux-usb@vger.kernel.org References: <20200211174126.GA29960@embeddedor> <20200211183229.GA1938663@kroah.com> <3fdbb16a-897c-aa5b-d45d-f824f6810412@embeddedor.com> <202002111129.77DB1CCC7B@keescook> <20200211193854.GA1972490@kroah.com> <88e09425-8207-7a1e-8802-886f9694a37f@embeddedor.com> <202002111210.876CEB6@keescook> From: "Gustavo A. R. Silva" Autocrypt: addr=gustavo@embeddedor.com; keydata= xsFNBFssHAwBEADIy3ZoPq3z5UpsUknd2v+IQud4TMJnJLTeXgTf4biSDSrXn73JQgsISBwG 2Pm4wnOyEgYUyJd5tRWcIbsURAgei918mck3tugT7AQiTUN3/5aAzqe/4ApDUC+uWNkpNnSV tjOx1hBpla0ifywy4bvFobwSh5/I3qohxDx+c1obd8Bp/B/iaOtnq0inli/8rlvKO9hp6Z4e DXL3PlD0QsLSc27AkwzLEc/D3ZaqBq7ItvT9Pyg0z3Q+2dtLF00f9+663HVC2EUgP25J3xDd 496SIeYDTkEgbJ7WYR0HYm9uirSET3lDqOVh1xPqoy+U9zTtuA9NQHVGk+hPcoazSqEtLGBk YE2mm2wzX5q2uoyptseSNceJ+HE9L+z1KlWW63HhddgtRGhbP8pj42bKaUSrrfDUsicfeJf6 m1iJRu0SXYVlMruGUB1PvZQ3O7TsVfAGCv85pFipdgk8KQnlRFkYhUjLft0u7CL1rDGZWDDr NaNj54q2CX9zuSxBn9XDXvGKyzKEZ4NY1Jfw+TAMPCp4buawuOsjONi2X0DfivFY+ZsjAIcx qQMglPtKk/wBs7q2lvJ+pHpgvLhLZyGqzAvKM1sVtRJ5j+ARKA0w4pYs5a5ufqcfT7dN6TBk LXZeD9xlVic93Ju08JSUx2ozlcfxq+BVNyA+dtv7elXUZ2DrYwARAQABzSxHdXN0YXZvIEEu IFIuIFNpbHZhIDxndXN0YXZvQGVtYmVkZGVkb3IuY29tPsLBfQQTAQgAJwUCWywcDAIbIwUJ CWYBgAULCQgHAgYVCAkKCwIEFgIDAQIeAQIXgAAKCRBHBbTLRwbbMZ6tEACk0hmmZ2FWL1Xi l/bPqDGFhzzexrdkXSfTTZjBV3a+4hIOe+jl6Rci/CvRicNW4H9yJHKBrqwwWm9fvKqOBAg9 obq753jydVmLwlXO7xjcfyfcMWyx9QdYLERTeQfDAfRqxir3xMeOiZwgQ6dzX3JjOXs6jHBP cgry90aWbaMpQRRhaAKeAS14EEe9TSIly5JepaHoVdASuxklvOC0VB0OwNblVSR2S5i5hSsh ewbOJtwSlonsYEj4EW1noQNSxnN/vKuvUNegMe+LTtnbbocFQ7dGMsT3kbYNIyIsp42B5eCu JXnyKLih7rSGBtPgJ540CjoPBkw2mCfhj2p5fElRJn1tcX2McsjzLFY5jK9RYFDavez5w3lx JFgFkla6sQHcrxH62gTkb9sUtNfXKucAfjjCMJ0iuQIHRbMYCa9v2YEymc0k0RvYr43GkA3N PJYd/vf9vU7VtZXaY4a/dz1d9dwIpyQARFQpSyvt++R74S78eY/+lX8wEznQdmRQ27kq7BJS R20KI/8knhUNUJR3epJu2YFT/JwHbRYC4BoIqWl+uNvDf+lUlI/D1wP+lCBSGr2LTkQRoU8U 64iK28BmjJh2K3WHmInC1hbUucWT7Swz/+6+FCuHzap/cjuzRN04Z3Fdj084oeUNpP6+b9yW e5YnLxF8ctRAp7K4yVlvA87BTQRbLBwMARAAsHCE31Ffrm6uig1BQplxMV8WnRBiZqbbsVJB H1AAh8tq2ULl7udfQo1bsPLGGQboJSVN9rckQQNahvHAIK8ZGfU4Qj8+CER+fYPp/MDZj+t0 DbnWSOrG7z9HIZo6PR9z4JZza3Hn/35jFggaqBtuydHwwBANZ7A6DVY+W0COEU4of7CAahQo 5NwYiwS0lGisLTqks5R0Vh+QpvDVfuaF6I8LUgQR/cSgLkR//V1uCEQYzhsoiJ3zc1HSRyOP otJTApqGBq80X0aCVj1LOiOF4rrdvQnj6iIlXQssdb+WhSYHeuJj1wD0ZlC7ds5zovXh+FfF l5qH5RFY/qVn3mNIVxeO987WSF0jh+T5ZlvUNdhedGndRmwFTxq2Li6GNMaolgnpO/CPcFpD jKxY/HBUSmaE9rNdAa1fCd4RsKLlhXda+IWpJZMHlmIKY8dlUybP+2qDzP2lY7kdFgPZRU+e zS/pzC/YTzAvCWM3tDgwoSl17vnZCr8wn2/1rKkcLvTDgiJLPCevqpTb6KFtZosQ02EGMuHQ I6Zk91jbx96nrdsSdBLGH3hbvLvjZm3C+fNlVb9uvWbdznObqcJxSH3SGOZ7kCHuVmXUcqoz ol6ioMHMb+InrHPP16aVDTBTPEGwgxXI38f7SUEn+NpbizWdLNz2hc907DvoPm6HEGCanpcA EQEAAcLBZQQYAQgADwUCWywcDAIbDAUJCWYBgAAKCRBHBbTLRwbbMdsZEACUjmsJx2CAY+QS UMebQRFjKavwXB/xE7fTt2ahuhHT8qQ/lWuRQedg4baInw9nhoPE+VenOzhGeGlsJ0Ys52sd XvUjUocKgUQq6ekOHbcw919nO5L9J2ejMf/VC/quN3r3xijgRtmuuwZjmmi8ct24TpGeoBK4 WrZGh/1hAYw4ieARvKvgjXRstcEqM5thUNkOOIheud/VpY+48QcccPKbngy//zNJWKbRbeVn imua0OpqRXhCrEVm/xomeOvl1WK1BVO7z8DjSdEBGzbV76sPDJb/fw+y+VWrkEiddD/9CSfg fBNOb1p1jVnT2mFgGneIWbU0zdDGhleI9UoQTr0e0b/7TU+Jo6TqwosP9nbk5hXw6uR5k5PF 8ieyHVq3qatJ9K1jPkBr8YWtI5uNwJJjTKIA1jHlj8McROroxMdI6qZ/wZ1ImuylpJuJwCDC ORYf5kW61fcrHEDlIvGc371OOvw6ejF8ksX5+L2zwh43l/pKkSVGFpxtMV6d6J3eqwTafL86 YJWH93PN+ZUh6i6Rd2U/i8jH5WvzR57UeWxE4P8bQc0hNGrUsHQH6bpHV2lbuhDdqo+cM9eh GZEO3+gCDFmKrjspZjkJbB5Gadzvts5fcWGOXEvuT8uQSvl+vEL0g6vczsyPBtqoBLa9SNrS VtSixD1uOgytAP7RWS474w== Message-ID: <2b73d115-1259-24ae-6f56-e3aa12e5e408@embeddedor.com> Date: Tue, 11 Feb 2020 14:30:17 -0600 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.4.1 MIME-Version: 1.0 In-Reply-To: <202002111210.876CEB6@keescook> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-AntiAbuse: This header was added to track abuse, please include it with any abuse report X-AntiAbuse: Primary Hostname - gator4166.hostgator.com X-AntiAbuse: Original Domain - vger.kernel.org X-AntiAbuse: Originator/Caller UID/GID - [47 12] / [47 12] X-AntiAbuse: Sender Address Domain - embeddedor.com X-BWhitelist: no X-Source-IP: 200.68.140.36 X-Source-L: No X-Exim-ID: 1j1c8F-001jRM-5K X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: ([192.168.43.131]) [200.68.140.36]:27441 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 21 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2/11/20 14:12, Kees Cook wrote: > On Tue, Feb 11, 2020 at 01:54:22PM -0600, Gustavo A. R. Silva wrote: >> >> >> On 2/11/20 13:38, Greg KH wrote: >>> On Tue, Feb 11, 2020 at 11:32:04AM -0800, Kees Cook wrote: >>>> On Tue, Feb 11, 2020 at 01:20:36PM -0600, Gustavo A. R. Silva wrote: >>>>> >>>>> >>>>> On 2/11/20 12:32, Greg KH wrote: >>>>>> On Tue, Feb 11, 2020 at 11:41:26AM -0600, Gustavo A. R. Silva wrote: >>>>>>> The current codebase makes use of the zero-length array language >>>>>>> extension to the C90 standard, but the preferred mechanism to declare >>>>>>> variable-length types such as these ones is a flexible array member[1][2], >>>>>>> introduced in C99: >>>>>>> >>>>>>> struct foo { >>>>>>> int stuff; >>>>>>> struct boo array[]; >>>>>>> }; >>>>>>> >>>>>>> By making use of the mechanism above, we will get a compiler warning >>>>>>> in case the flexible array does not occur last in the structure, which >>>>>>> will help us prevent some kind of undefined behavior bugs from being >>>>>>> unadvertenly introduced[3] to the codebase from now on. >>>>>>> >>>>>>> All these instances of code were found with the help of the following >>>>>>> Coccinelle script: >>>>>>> >>>>>>> @@ >>>>>>> identifier S, member, array; >>>>>>> type T1, T2; >>>>>>> @@ >>>>>>> >>>>>>> struct S { >>>>>>> ... >>>>>>> T1 member; >>>>>>> T2 array[ >>>>>>> - 0 >>>>>>> ]; >>>>>>> }; >>>>>>> >>>>>>> [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html >>>>>>> [2] https://github.com/KSPP/linux/issues/21 >>>>>>> [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour") >>>>>>> >>>>>>> NOTE: I'll carry this in my -next tree for the v5.6 merge window. >>>>>> >>>>>> Why not carve this up into per-subsystem patches so that we can apply >>>>>> them to our 5.7-rc1 trees and then you submit the "remaining" that don't >>>>>> somehow get merged at that timeframe for 5.7-rc2? >>>>>> >>>>> >>>>> Yep, sounds good. I'll do that. >>>> >>>> FWIW, I'd just like to point out that since this is a mechanical change >>>> with no code generation differences (unlike the pre-C90 1-byte array >>>> conversions), it's a way better use of everyone's time to just splat >>>> this in all at once. >>>> >>>> That said, it looks like Gustavo is up for it, but I'd like us to >>>> generally consider these kinds of mechanical changes as being easier to >>>> manage in a single patch. (Though getting Acks tends to be a bit >>>> harder...) >>> >>> Hey, if this is such a mechanical patch, let's get it to Linus now, >>> what's preventing that from being merged now? > > Now would be a good time, yes. (Linus has wanted Acks for such things > sometimes, but those were more "risky" changes...) > >> Well, the only thing is that this has never been in linux-next. > > Hmm. Was it in one of your 0day-tested trees? > It was in my tree for quite a while, but it was never 0day-tested. Just recently, the 0day guys started testing my _new_ branches, regularly. Today, I updated my -next branch to v5.6-rc1 and added the treewide patch. So, I expect it to be 0day-tested in a couple of days. -- Gustavo