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 89166C001DE for ; Wed, 19 Jul 2023 13:03:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230281AbjGSNDm (ORCPT ); Wed, 19 Jul 2023 09:03:42 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38964 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230429AbjGSNDk (ORCPT ); Wed, 19 Jul 2023 09:03:40 -0400 Received: from mail-qk1-x734.google.com (mail-qk1-x734.google.com [IPv6:2607:f8b0:4864:20::734]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 42F81172E for ; Wed, 19 Jul 2023 06:03:38 -0700 (PDT) Received: by mail-qk1-x734.google.com with SMTP id af79cd13be357-766fd5f9536so465260885a.3 for ; Wed, 19 Jul 2023 06:03:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bobcopeland-com.20221208.gappssmtp.com; s=20221208; t=1689771817; x=1690376617; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:from:to:cc:subject:date:message-id:reply-to; bh=yVmx1ErmKUSGwgpTmxJxNkC1cHItIhkWOY1t2BSjV8Q=; b=WFIm/wT7DIsM2va5wLeq8CeKKISvdlWhpi3HN+9y/jdkErtnpEBWsFnlIYC3IVDwG0 mC1khj0qrSP/kEAyX6fwU0YVQIQB8en2StaQ2WQbIOd03DJVdf8vBu40fDg2fhUZ3Iya vsUTwWE8xMHbYlcMggNZFnGmqMmkvUDXCGi/dcWKrDIIUV05yyrViqUcZjZXgXAs3MFp F8jPmDUlpEWP9kaE+GW3dDUGXjER9RyBdAnx5Ta8BSYVGjzWmbxO1a+vOkGT+0pFW9wV jbbLO4caVbytKmzcYKfONV14noUDYHhxE16n0pJu4wVlDT2BhK4D7znHa6rnpEM5mVMb bknQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689771817; x=1690376617; h=in-reply-to:content-disposition:mime-version:references:message-id :subject:cc:to:from:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to; bh=yVmx1ErmKUSGwgpTmxJxNkC1cHItIhkWOY1t2BSjV8Q=; b=jqZNDoejxAmk/rU9avQvdNwkxDV41WDlm2u1wvRj80Q62mhDXLCF+eqm6ejeLVLKNK J7/uz8I57tKAVD3piFAhVPVV5ck7enkscYjG276l6rxnKaRId/3u8EquDH1pg6j7sBo8 8f7bkIbJEYDD78aEqBM1M9/QYFGoMPWW/+SwQLjbrR1DTq0luGPYZSaoOqQ/JvNFpdFx TpdYZhek1txxcF0x3n6v+Hcp0LUv/8cTRkUiIj4Hx4ofKcVtmBEIcFnG/ScKyX85PqAj IBTuIKQ/b7w/+mfH7BeddlQ2qATGk1aEkLEyRdYC5lL5Fl5p0kx5dZk5jJ6D9fQ/epYc L8Wg== X-Gm-Message-State: ABy/qLafoPXLGkxpXqEcpRiA6OJl1LZiunDBEwEZOSrvSQI81BkxKCXX Ko95ea9Gm4hiBQ9nHRgfU9qWig== X-Google-Smtp-Source: APBJJlHzFO1toSuIggCnLfxp/n3DCsCdhlZJjY2lZmt7rAuvGM36jSqUMtKNKbbu5dW0OQoTiqhnGg== X-Received: by 2002:a05:620a:bc5:b0:768:158a:bc0 with SMTP id s5-20020a05620a0bc500b00768158a0bc0mr2646464qki.39.1689771817272; Wed, 19 Jul 2023 06:03:37 -0700 (PDT) Received: from elrond.bobcopeland.com ([142.115.123.76]) by smtp.gmail.com with ESMTPSA id r25-20020a05620a03d900b007623c96430csm1244845qkm.111.2023.07.19.06.03.36 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 19 Jul 2023 06:03:36 -0700 (PDT) Received: by elrond.bobcopeland.com (Postfix, from userid 1000) id 74E8EFC0158; Wed, 19 Jul 2023 09:03:29 -0400 (EDT) Date: Wed, 19 Jul 2023 09:03:29 -0400 From: Bob Copeland To: Kees Cook Cc: "Gustavo A. R. Silva" , linux-karma-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH][next] fs: omfs: Use flexible-array member in struct omfs_extent Message-ID: References: <202307170758.14B5D83D@keescook> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <202307170758.14B5D83D@keescook> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 17, 2023 at 08:20:22AM -0700, Kees Cook wrote: > > @@ -14,7 +14,7 @@ static u32 omfs_max_extents(struct omfs_sb_info *sbi, int offset) > > { > > return (sbi->s_sys_blocksize - offset - > > sizeof(struct omfs_extent)) / > > - sizeof(struct omfs_extent_entry) + 1; > > + sizeof(struct omfs_extent_entry); > > } > > I think the original calculation meant to do: > > return (sbi->s_sys_blocksize - offset - > (sizeof(struct omfs_extent) - sizeof(struct omfs_extent_entry))) / > sizeof(struct omfs_extent_entry); I can confirm the intent. I also went back and looked at the usages just to be sure. In this case, there are two possible values for x = s_sys_blocksize - offset: 7728 or 8128, and both can be divided by 16 evenly so you have either: f_old = (x - 32) / 16 + 1 or: f_new = (x - 16) / 16 they both simplify to x/16 - 1 so they are equivalent for these inputs. -- Bob Copeland %% https://bobcopeland.com/