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=-15.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=unavailable 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 47BD3C433EF for ; Tue, 21 Sep 2021 00:40:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1D0F561245 for ; Tue, 21 Sep 2021 00:40:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232179AbhIUAl6 (ORCPT ); Mon, 20 Sep 2021 20:41:58 -0400 Received: from gateway24.websitewelcome.com ([192.185.51.61]:21236 "EHLO gateway24.websitewelcome.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233095AbhIUAj5 (ORCPT ); Mon, 20 Sep 2021 20:39:57 -0400 X-Greylist: delayed 1481 seconds by postgrey-1.27 at vger.kernel.org; Mon, 20 Sep 2021 20:39:57 EDT Received: from cm11.websitewelcome.com (cm11.websitewelcome.com [100.42.49.5]) by gateway24.websitewelcome.com (Postfix) with ESMTP id B71F337E4 for ; Mon, 20 Sep 2021 19:13:48 -0500 (CDT) Received: from gator4166.hostgator.com ([108.167.133.22]) by cmsmtp with SMTP id STPwm2MTvK61iSTPwmBZCl; Mon, 20 Sep 2021 19:13:48 -0500 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=rC43D1q/Fpqld09/wg6gq0zwktyAt7L1OzENn3Bvg8g=; b=Rbx+WldhwvBXH/Es+i84gO7nK4 xhaunjLemgYxJF41YiEYkZr5b0L2FbetCIHtYE2BoWoEkd1SpLXQerryMdzvCBKd5gR1Fk23806gt SG/UWujtSucxy/Jro+J6BYpM28UjAra1tMQI3oYevYp0uY/xt1r7X/F9jh2zJXCc5L6Sb0iT4VOzq zeciwVEm181eJlLV//Opy8hORo42OYOEuO9bX8ZqdTMHPqi5jDXYS+inQETnwkg1dapIobiP++PKQ cGF/OGlvt5ZeBLwo7CKfy5nGbEHOxCZnVPS0m6Fr1HvSyPqbckZMPf0uHFKkHu/XrrSgiIBYsAkGN q+0B8dUg==; Received: from 187-162-31-110.static.axtel.net ([187.162.31.110]:34200 helo=[192.168.15.9]) by gator4166.hostgator.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.94.2) (envelope-from ) id 1mSTPw-000oJG-Bi; Mon, 20 Sep 2021 19:13:48 -0500 Subject: Re: [PATCH] writeback: prefer struct_size over open coded arithmetic To: Len Baker , Alexander Viro Cc: Kees Cook , "Gustavo A. R. Silva" , linux-fsdevel@vger.kernel.org, linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org References: <20210919094630.30668-1-len.baker@gmx.com> From: "Gustavo A. R. Silva" Message-ID: <6bc45138-c3a5-9465-40cb-3db714e7706d@embeddedor.com> Date: Mon, 20 Sep 2021 19:17:36 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.13.0 MIME-Version: 1.0 In-Reply-To: <20210919094630.30668-1-len.baker@gmx.com> 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: 187.162.31.110 X-Source-L: No X-Exim-ID: 1mSTPw-000oJG-Bi X-Source: X-Source-Args: X-Source-Dir: X-Source-Sender: 187-162-31-110.static.axtel.net ([192.168.15.9]) [187.162.31.110]:34200 X-Source-Auth: gustavo@embeddedor.com X-Email-Count: 33 X-Source-Cap: Z3V6aWRpbmU7Z3V6aWRpbmU7Z2F0b3I0MTY2Lmhvc3RnYXRvci5jb20= X-Local-Domain: yes Precedence: bulk List-ID: X-Mailing-List: linux-hardening@vger.kernel.org On 9/19/21 04:46, Len Baker wrote: > As noted in the "Deprecated Interfaces, Language Features, Attributes, > and Conventions" documentation [1], size calculations (especially > multiplication) should not be performed in memory allocator (or similar) > function arguments due to the risk of them overflowing. This could lead > to values wrapping around and a smaller allocation being made than the > caller was expecting. Using those allocations could lead to linear > overflows of heap memory and other misbehaviors. > > In this case this is not actually dynamic size: all the operands > involved in the calculation are constant values. However it is best to > refactor this anyway, just to keep the open-coded math idiom out of > code. > > So, use the struct_size() helper to do the arithmetic instead of the > argument "size + count * size" in the kzalloc() function. > > [1] https://www.kernel.org/doc/html/latest/process/deprecated.html#open-coded-arithmetic-in-allocator-arguments > > Signed-off-by: Len Baker > --- > fs/fs-writeback.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c > index 81ec192ce067..f7abff31e026 100644 > --- a/fs/fs-writeback.c > +++ b/fs/fs-writeback.c > @@ -624,8 +624,8 @@ bool cleanup_offline_cgwb(struct bdi_writeback *wb) > int nr; > bool restart = false; > > - isw = kzalloc(sizeof(*isw) + WB_MAX_INODES_PER_ISW * > - sizeof(struct inode *), GFP_KERNEL); > + isw = kzalloc(struct_size(isw, inodes, WB_MAX_INODES_PER_ISW), > + GFP_KERNEL); There is another instance at: 569 isw = kzalloc(sizeof(*isw) + 2 * sizeof(struct inode *), GFP_ATOMIC); 570 if (!isw) 571 return; If you are finding these with the help of Coccinelle, please mention it in the changelog text. :) Thanks -- Gustavo > if (!isw) > return restart; > > -- > 2.25.1 >