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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=no 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 6787CC7618B for ; Fri, 26 Jul 2019 15:05:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4A87521901 for ; Fri, 26 Jul 2019 15:05:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2387716AbfGZPFh (ORCPT ); Fri, 26 Jul 2019 11:05:37 -0400 Received: from mx2.suse.de ([195.135.220.15]:54518 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1727287AbfGZPFg (ORCPT ); Fri, 26 Jul 2019 11:05:36 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id B3D96ADF1; Fri, 26 Jul 2019 15:05:34 +0000 (UTC) Received: by ds.suse.cz (Postfix, from userid 10065) id 85BAADA811; Fri, 26 Jul 2019 17:06:10 +0200 (CEST) Date: Fri, 26 Jul 2019 17:06:09 +0200 From: David Sterba To: Qu Wenruo Cc: Jia-Ju Bai , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] fs: btrfs: Fix a possible null-pointer dereference in insert_inline_extent() Message-ID: <20190726150609.GE2868@twin.jikos.cz> Reply-To: dsterba@suse.cz Mail-Followup-To: dsterba@suse.cz, Qu Wenruo , Jia-Ju Bai , clm@fb.com, josef@toxicpanda.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org References: <20190724021132.27378-1-baijiaju1990@gmail.com> <800ae777-928f-2969-d4dd-6f358a039e48@gmail.com> <1b708c0d-8ea1-3898-0340-9cbce1fc2602@gmx.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <1b708c0d-8ea1-3898-0340-9cbce1fc2602@gmx.com> User-Agent: Mutt/1.5.23.1 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 24, 2019 at 10:57:24AM +0800, Qu Wenruo wrote: > On 2019/7/24 上午10:33, Jia-Ju Bai wrote: > > On 2019/7/24 10:21, Qu Wenruo wrote: > >> On 2019/7/24 上午10:11, Jia-Ju Bai wrote: > >>> In insert_inline_extent(), there is an if statement on line 181 to check > >>> whether compressed_pages is NULL: > >>>      if (compressed_size && compressed_pages) > >>> > >>> When compressed_pages is NULL, compressed_pages is used on line 215: > >>>      cpage = compressed_pages[i]; > >>> > >>> Thus, a possible null-pointer dereference may occur. > >>> > >>> To fix this possible bug, compressed_pages is checked on line 214. > >> This can only be hit with compressed_size > 0 and compressed_pages != > >> NULL. > >> > >> It would be better to have an extra ASSERT() to warn developers about > >> the impossible case. > > > > Thanks for the reply :) > > So I should add ASSERT(compressed_size > 0 & compressed_pages) at the > > beginning of the function, and remove "if (compressed_size && > > compressed_pages)"? > > My suggestion is, ASSERT((compressed_size >0 && compressed_pages) || > (compressed_size == 0 && !compressed_pages)) > > And keeps the original checks. > > Anyway, just a suggestion. Agreed, the assertion would be good, covering both cases in one statement at the beginning of the function.