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=-5.3 required=3.0 tests=BAYES_00, 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 C0DCEC433ED for ; Tue, 18 May 2021 18:32:14 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9AF4460D07 for ; Tue, 18 May 2021 18:32:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1351593AbhERSdb (ORCPT ); Tue, 18 May 2021 14:33:31 -0400 Received: from youngberry.canonical.com ([91.189.89.112]:58911 "EHLO youngberry.canonical.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234536AbhERSdb (ORCPT ); Tue, 18 May 2021 14:33:31 -0400 Received: from 1.general.cking.uk.vpn ([10.172.193.212]) by youngberry.canonical.com with esmtpsa (TLS1.2) tls TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256 (Exim 4.93) (envelope-from ) id 1lj4Vo-0006zx-1L; Tue, 18 May 2021 18:32:12 +0000 To: Tong Zhang , Greg Kroah-Hartman From: Colin Ian King Subject: re: misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge Cc: Arnd Bergmann , "linux-kernel@vger.kernel.org" Message-ID: Date: Tue, 18 May 2021 19:32:11 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hi, Static analysis on linux-next with Coverity has detected an issue in drivers/misc/cardreader/alcor_pci.c in function alcor_pci_init_check_aspm with the following commit: commit 3ce3e45cc333da707d4d6eb433574b990bcc26f5 Author: Tong Zhang Date: Thu May 13 00:07:33 2021 -0400 misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge The analysis is as follows: 135 static void alcor_pci_init_check_aspm(struct alcor_pci_priv *priv) 136 { 137 struct pci_dev *pci; 138 int where; 139 u32 val32; 140 141 priv->pdev_cap_off = alcor_pci_find_cap_offset(priv, priv->pdev); 142 /* 143 * A device might be attached to root complex directly and 144 * priv->parent_pdev will be NULL. In this case we don't check its 145 * capability and disable ASPM completely. 146 */ 1. Condition !priv->parent_pdev, taking true branch. 2. var_compare_op: Comparing priv->parent_pdev to null implies that priv->parent_pdev might be null. 147 if (!priv->parent_pdev) Dereference after null check (FORWARD_NULL) 3. var_deref_model: Passing null pointer priv->parent_pdev to alcor_pci_find_cap_offset, which dereferences it. 148 priv->parent_cap_off = alcor_pci_find_cap_offset(priv, 149 priv->parent_pdev); When !priv->parent_pdev is true, then priv->parent_pdev is NULL and hence the call to alcor_pci_find_cap_offset() is dereferencing a null pointer in the priv->parent_pdev argument. I suspect the logic in the if statement is inverted, the ! should be removed. This seems too trivial to be wrong. Maybe I'm missing something deeper. Colin