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=-2.4 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT 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 DF8A8C43381 for ; Mon, 11 Mar 2019 17:10:12 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id AD99A2075C for ; Mon, 11 Mar 2019 17:10:12 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="eyhZnsyz" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727592AbfCKRKL (ORCPT ); Mon, 11 Mar 2019 13:10:11 -0400 Received: from mail-wr1-f68.google.com ([209.85.221.68]:41834 "EHLO mail-wr1-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726864AbfCKRKK (ORCPT ); Mon, 11 Mar 2019 13:10:10 -0400 Received: by mail-wr1-f68.google.com with SMTP id p1so1503884wrs.8 for ; Mon, 11 Mar 2019 10:10:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=MzgqU2PlXs330QQdmskA3r2zVUJBgkkVKy68/kbmpZM=; b=eyhZnsyz6ka6Prn2IED8nli5+vlW53eGwasip71b3t2FFVJdL3aQE15FgaqBHQw5hd GZ5DjM2WN5QhRfsaxjIJ4MjO9Db5ly8gSFNXsi9h6Ky2Z4CzFmH0+7OT8CEw8Ss0UZyY hFsaagjhDA522dCsKIEFjYslhUztVmADt+DZrqcbEQG4iUsyApBlXVZZJJ+jeQXjqgI2 v/VWaFnF4xBUmhTa1zfhGSR+guyqroAIcNWKEIzAlUvVovEyxe1r7a7AZdNDNPLrkSj2 D6rgiR2kAnnPco4DDk72PCpthqFlLVcGH+T+Ws5fx05YLlt29Wmijnu6vmk4+ug7sgo7 ZfYQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to:user-agent; bh=MzgqU2PlXs330QQdmskA3r2zVUJBgkkVKy68/kbmpZM=; b=BWokydacjSMEE5NnXi0qssQm6TzLS3GZC99pJ8JOEZY9GvNlw+mhrkrUnxTf8QmWnj uHL3fTum+HNI4oenqRt1XKhWLm+skeuRxXNQsJkQkNK8uZeJxghgOgk0cpYOALpzRuNW 1dPX28Ph8v1QRm27VEyib5WLo2lK15nd8C8mniD3JR9hGeLcVb3mYjSimy8o8z9aOpus 5DyyaeYNr2pbQeo4LTk2C9ZAMsEJQhn56XzrsIdYpCsmZrKjKuDMx586KrgTcnIucZf+ +TgchXP1aW02g1XhfUKRvm8rJRbkkt9X9cXqX/4IE8Ok24ovXnMK7HeEOAk8yu4M5+4X /K0Q== X-Gm-Message-State: APjAAAUyYLCEVRRLAjmN8rZnKBqi+dRcT62xLxTo4DaAOQxmf5kZi86t VnD8MKvykMhsLklzES2ItARrWN4= X-Google-Smtp-Source: APXvYqwBVSuFHBZjiIKCSHYwTbpEripNZa7A6jYYRG8mYGWDhtDek3ihBNfQxVitb6pKqUNjnJRUMQ== X-Received: by 2002:a5d:6643:: with SMTP id f3mr709919wrw.120.1552324208947; Mon, 11 Mar 2019 10:10:08 -0700 (PDT) Received: from avx2 ([46.53.240.176]) by smtp.gmail.com with ESMTPSA id y13sm7433524wrw.31.2019.03.11.10.10.07 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 11 Mar 2019 10:10:08 -0700 (PDT) Date: Mon, 11 Mar 2019 20:10:06 +0300 From: Alexey Dobriyan To: Pavel Machek Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/4] elf: don't be afraid of overflow Message-ID: <20190311171006.GA2141@avx2> References: <20190204202715.GA27482@avx2> <20190311110423.GC14118@amd> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190311110423.GC14118@amd> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 11, 2019 at 12:04:23PM +0100, Pavel Machek wrote: > On Mon 2019-02-04 23:27:15, Alexey Dobriyan wrote: > > Number of ELF program headers is 16-bit by spec, so total size > > comfortably fits into "unsigned int". > > If it can't overflow, gcc should know too, and optimize checks > out... right? Turns out it doesn't. > > @@ -429,13 +430,9 @@ static struct elf_phdr *load_elf_phdrs(struct elfhdr *elf_ex, > > goto out; > > > > /* Sanity check the number of program headers... */ > > - if (elf_ex->e_phnum < 1 || > > - elf_ex->e_phnum > 65536U / sizeof(struct elf_phdr)) > > - goto out; > > - > > /* ...and their total size. */ > > This is just wrong. You removed check for zero, and I'm pretty sure > sizeof() is not 1, so this one can trigger, too. No. ->e_phnum is 65535 max. size = sizeof(struct elf_phdr) * elf_ex->e_phnum; if (size == 0 || size > 65536 || size > ELF_MIN_ALIGN) goto out;