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=-12.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS 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 C421EC433ED for ; Mon, 10 May 2021 22:20:59 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 9FD2F614A5 for ; Mon, 10 May 2021 22:20:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233365AbhEJWV5 (ORCPT ); Mon, 10 May 2021 18:21:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57106 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230463AbhEJWVT (ORCPT ); Mon, 10 May 2021 18:21:19 -0400 Received: from mail-il1-x131.google.com (mail-il1-x131.google.com [IPv6:2607:f8b0:4864:20::131]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 928C1C061574 for ; Mon, 10 May 2021 15:20:13 -0700 (PDT) Received: by mail-il1-x131.google.com with SMTP id l19so15446152ilk.13 for ; Mon, 10 May 2021 15:20:13 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=FN6iTMK7hIktHgqpc3ijQCBqrZ7ymkqilRRyERzJDvQ=; b=L8xQzuassvepilB0T3g/2/n8rUnojrY5tdSLtg53gqWpHMXciFdQvy+Lpb/sDxRFJb Y1K2iMhw48lBTTNFo3Md3DUZvbvZfzHTj9+elm+IZ6K+om4luDBsTJQdPKM2CCl7KdyU ef6+Vs2ioXCRqh6ht44VLcga1OBAGqHC0Tt+t4f78HJ8vrI5uWVY0jhlW1K1ZIOsEUWd lStHRh8Ol+2lKzsPSPu8AJbCSoRfHBwiGwgGo0Vu0+kJe8C663G57N1NK+zYKxhFriUr 6Pd5LhM1WBdHViqiK9w4eCKi4LvtwOIhLugablxxRpH2/ytOBN8iubw0cjUJ3lMBsL/V s8CA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=FN6iTMK7hIktHgqpc3ijQCBqrZ7ymkqilRRyERzJDvQ=; b=qTA6CD1CAbz/256DxlNjraue89aq2xGeA7MaFuFzLXK9gYlZWqHx6jxLiU9dFhJGPS Gi2N8MpEGJcgfbo6sjSr6C5wWDwOo0ksXG5Yl4AReoDgfmXqXUpuXs0vKYBcS/mwicZI pNRRO3H1Y+5rCqSGIZVJ5UOfihwLTHoXiBNKabvqoMub4QYH1eu5lc0h8Vr5u1iivRsO BxmhE2TzXjW4a19YUoBvsoKecdN2Hzwc0VSVc/9xn+ct3PgZ4RfsRHpbmqhF7seDJhbY 0iqM7Ooct3jvtD5oLO5XEdgIv7KVUso0yuzDK2m58DLu5grbzNhgb2o9zG2/6D6qEsq5 yCPw== X-Gm-Message-State: AOAM530+WKJ4aOcnYn9bGAjRlixhxKQd7jlpwXwqSgs3jhhw7zZUQMlB rxKmjhmp8PQ5tcT/ygoEVYuHJB4WXroWZuf0/s2cUBJgL+Pv682u X-Google-Smtp-Source: ABdhPJyP9qSWNxy3zUAtBWjTSo93UqAgjrdvNCerFZGPU4OQFbWkOTaudyi/h5BG6qwux29+eAQ2XS7kO9S+82XtYB8= X-Received: by 2002:a92:c8d2:: with SMTP id c18mr23985639ilq.81.1620685213064; Mon, 10 May 2021 15:20:13 -0700 (PDT) MIME-Version: 1.0 References: <20210426220728.1230340-1-ztong0001@gmail.com> In-Reply-To: From: Tong Zhang Date: Mon, 10 May 2021 15:20:02 -0700 Message-ID: Subject: Re: [PATCH] misc: alcor_pci: fix null-ptr-deref when there is no PCI bridge To: Greg Kroah-Hartman Cc: Arnd Bergmann , open list Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, May 10, 2021 at 7:36 AM Greg Kroah-Hartman wrote: > > On Mon, Apr 26, 2021 at 06:07:27PM -0400, Tong Zhang wrote: > > the PCI bridge might be NULL, so we'd better check before use it > > > > [ 1.246492] BUG: kernel NULL pointer dereference, address: 00000000000000c0 > > [ 1.248731] RIP: 0010:pci_read_config_byte+0x5/0x40 > > [ 1.253998] Call Trace: > > [ 1.254131] ? alcor_pci_find_cap_offset.isra.0+0x3a/0x100 [alcor_pci] > > [ 1.254476] alcor_pci_probe+0x169/0x2d5 [alcor_pci] > > > > Signed-off-by: Tong Zhang > > --- > > drivers/misc/cardreader/alcor_pci.c | 3 +++ > > 1 file changed, 3 insertions(+) > > > > diff --git a/drivers/misc/cardreader/alcor_pci.c b/drivers/misc/cardreader/alcor_pci.c > > index cd402c89189e..1c33453fd5c7 100644 > > --- a/drivers/misc/cardreader/alcor_pci.c > > +++ b/drivers/misc/cardreader/alcor_pci.c > > @@ -102,6 +102,9 @@ static int alcor_pci_find_cap_offset(struct alcor_pci_priv *priv, > > u8 val8; > > u32 val32; > > > > + if (!pci) > > + return 0; > > + > > where = ALCOR_CAP_START_OFFSET; > > pci_read_config_byte(pci, where, &val8); > > if (!val8) > > -- > > 2.25.1 > > > > I do not understand, how can pci ever be NULL? There is only 1 way this Hi Greg, I think the problem is with priv->parent_pdev = pdev->bus->self where bus->self can be NULL. when bus->self is NULL, calling alcor_pci_find_cap_offset(priv, priv->parent_pdev) is equivalent to alcor_pci_find_cap_offset(priv, NULL) - Tong > function can be called, and it's through the alcor_pci_probe() call, > which should have always set up the parent and pci pointers that get > passed to this function. > > How can that not happen? If it can happen, then something earlier than > this should be fixed instead of papering over the root problem here. > > How did you duplicate the crash you list above? > > thanks, > > greg k-h