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=-14.8 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH,MAILING_LIST_MULTI,NICE_REPLY_A, SIGNED_OFF_BY,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 630ADC433E2 for ; Thu, 10 Sep 2020 12:42:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 0FB7020C09 for ; Thu, 10 Sep 2020 12:42:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728289AbgIJMm1 (ORCPT ); Thu, 10 Sep 2020 08:42:27 -0400 Received: from szxga07-in.huawei.com ([45.249.212.35]:35772 "EHLO huawei.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1730770AbgIJMfv (ORCPT ); Thu, 10 Sep 2020 08:35:51 -0400 Received: from DGGEMS412-HUB.china.huawei.com (unknown [172.30.72.59]) by Forcepoint Email with ESMTP id 135462F4C83CA4C34600; Thu, 10 Sep 2020 20:35:18 +0800 (CST) Received: from [10.174.178.248] (10.174.178.248) by smtp.huawei.com (10.3.19.212) with Microsoft SMTP Server (TLS) id 14.3.487.0; Thu, 10 Sep 2020 20:35:13 +0800 Subject: Re: [PATCH] drm/mm: prevent a potential null-pointer dereference To: =?UTF-8?Q?Christian_K=c3=b6nig?= , , , , , , References: <20200910023858.43759-1-jingxiangfeng@huawei.com> CC: , From: Jing Xiangfeng Message-ID: <5F5A1D80.2060902@huawei.com> Date: Thu, 10 Sep 2020 20:35:12 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:38.0) Gecko/20100101 Thunderbird/38.1.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.178.248] X-CFilter-Loop: Reflected Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2020/9/10 16:58, Christian König wrote: > Am 10.09.20 um 04:38 schrieb Jing Xiangfeng: >> The macro 'DECLARE_NEXT_HOLE_ADDR' may hit a potential null-pointer >> dereference. So use 'entry' after checking it. > > I don't see a potential null-pointer dereference here. > > Where should that be? In current code，the "entry" pointer is checked after entry->rb_hole_addr. Thanks > > Christian. > >> >> Fixes: 5fad79fd66ff ("drm/mm: cleanup and improve next_hole_*_addr()") >> Signed-off-by: Jing Xiangfeng >> --- >> drivers/gpu/drm/drm_mm.c | 7 +++++-- >> 1 file changed, 5 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/gpu/drm/drm_mm.c b/drivers/gpu/drm/drm_mm.c >> index a4a04d246135..6fcf70f71962 100644 >> --- a/drivers/gpu/drm/drm_mm.c >> +++ b/drivers/gpu/drm/drm_mm.c >> @@ -392,11 +392,14 @@ first_hole(struct drm_mm *mm, >> #define DECLARE_NEXT_HOLE_ADDR(name, first, last) \ >> static struct drm_mm_node *name(struct drm_mm_node *entry, u64 >> size) \ >> { \ >> - struct rb_node *parent, *node = &entry->rb_hole_addr; \ >> + struct rb_node *parent, *node; \ >> \ >> - if (!entry || RB_EMPTY_NODE(node)) \ >> + if (!entry) \ >> return NULL; \ >> \ >> + node = &entry->rb_hole_addr; \ >> + if (RB_EMPTY_NODE(node)) \ >> + return NULL; \ >> if (usable_hole_addr(node->first, size)) { \ >> node = node->first; \ >> while (usable_hole_addr(node->last, size)) \ > > . >