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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id E92BECCA473 for ; Mon, 27 Jun 2022 16:37:19 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234392AbiF0QhT (ORCPT ); Mon, 27 Jun 2022 12:37:19 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35950 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234815AbiF0QhS (ORCPT ); Mon, 27 Jun 2022 12:37:18 -0400 Received: from mail-yw1-f175.google.com (mail-yw1-f175.google.com [209.85.128.175]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E374C1114B; Mon, 27 Jun 2022 09:37:17 -0700 (PDT) Received: by mail-yw1-f175.google.com with SMTP id 00721157ae682-3137316bb69so90988597b3.10; Mon, 27 Jun 2022 09:37:17 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=/8cJy4YWWhfOgGW+zMoAe8mZCw8P609Jt5k6gJA927w=; b=Cwn1H2Vq9sYafq7PTMKVTTBSnoMJbNpHkhdMU0Xkx8gbPCw2V44n4mL/aT6kRgcz+g 1ZR+lPQyrLj1yZfCUO/OM0bcJfUhGHAS0PI6TnV9Ppuap9sORGI2Td9LjuMLxDqZo9Wv /hAuvp4fLAiVB5vxZQr8rYspY9atwnf6vHxUZMOsUcwWyE1egYSgLCuECKlVCL18azqI qVx71z+2m0fQKn9jtiNGRcHvh3pKOWeKSA9bJdwXIpRGXpfLbintw4jJLGxfFxxjW21r 1bTIB/T1CKjWRnsYVcDGbsgGxgHN1irvyB4CLffWTqlKSiZ0CUETUZYKevIGVjxK+w4q bF5g== X-Gm-Message-State: AJIora//f6Y4n7SJ185Fpl7lLZXp3aoMgaq7wm2MxQ1C7wvUsGcwsNAa 3CUaIaCg4P8hdIjjokDaJKmsYZD7wTxvYTaBcaD4h9WI X-Google-Smtp-Source: AGRyM1usIXDdm9P7SB54q/8t5ltXdx4rqEoeT9ry649tveDiSQ//6tBKU1RbXt9fqmxaCge04BSuTw3NHSIIn0cV4Ho= X-Received: by 2002:a81:57d7:0:b0:317:b111:34d5 with SMTP id l206-20020a8157d7000000b00317b11134d5mr15951942ywb.7.1656347837101; Mon, 27 Jun 2022 09:37:17 -0700 (PDT) MIME-Version: 1.0 References: <20220428142854.1065953-1-gregkh@linuxfoundation.org> <20220428155858.GA14614@bhelgaas> In-Reply-To: From: "Rafael J. Wysocki" Date: Mon, 27 Jun 2022 18:37:06 +0200 Message-ID: Subject: Re: [PATCH] PCI/ACPI: do not reference a pci device after it has been released To: Greg Kroah-Hartman Cc: "Rafael J. Wysocki" , Bjorn Helgaas , Bjorn Helgaas , Linux Kernel Mailing List , Len Brown , Linux PCI , ACPI Devel Maling List , whitehat002 Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Mon, Jun 27, 2022 at 5:07 PM Greg Kroah-Hartman wrote: > > On Thu, Apr 28, 2022 at 10:30:38PM +0200, Rafael J. Wysocki wrote: > > On Thu, Apr 28, 2022 at 10:15 PM Rafael J. Wysocki wrote: > > > > > > On Thu, Apr 28, 2022 at 6:22 PM Greg Kroah-Hartman > > > wrote: > > > > > > > > On Thu, Apr 28, 2022 at 10:58:58AM -0500, Bjorn Helgaas wrote: > > > > > On Thu, Apr 28, 2022 at 04:28:53PM +0200, Greg Kroah-Hartman wrote: > > > > > > In acpi_get_pci_dev(), the debugging message for when a PCI bridge is > > > > > > not found uses a pointer to a pci device whose reference has just been > > > > > > dropped. The chance that this really is a device that is now been > > > > > > removed from the system is almost impossible to happen, but to be safe, > > > > > > let's print out the debugging message based on the acpi root device > > > > > > which we do have a valid reference to at the moment. > > > > > > > > > > This code was added by 497fb54f578e ("ACPI / PCI: Fix NULL pointer > > > > > dereference in acpi_get_pci_dev() (rev. 2)"). Not sure if it's worth > > > > > a Fixes: tag. > > > > > > > > Can't hurt, I'll add it for the v2 based on this review. > > > > > > > > > > > > > > acpi_get_pci_dev() is used by only five callers, three of which are > > > > > video/backlight related. I'm always skeptical of one-off interfaces > > > > > like this, but I don't know enough to propose any refactoring or other > > > > > alternatives. > > > > > > > > > > I'll leave this for Rafael, but if I were applying I would silently > > > > > touch up the subject to match convention: > > > > > > > > > > PCI/ACPI: Do not reference PCI device after it has been released > > > > > > > > Much simpler, thanks. > > > > > > > > > > > > > > > Cc: Bjorn Helgaas > > > > > > Cc: "Rafael J. Wysocki" > > > > > > Cc: Len Brown > > > > > > Cc: linux-pci@vger.kernel.org > > > > > > Cc: linux-acpi@vger.kernel.org > > > > > > Reported-by: whitehat002 > > > > > > Signed-off-by: Greg Kroah-Hartman > > > > > > --- > > > > > > drivers/acpi/pci_root.c | 3 ++- > > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c > > > > > > index 6f9e75d14808..ecda378dbc09 100644 > > > > > > --- a/drivers/acpi/pci_root.c > > > > > > +++ b/drivers/acpi/pci_root.c > > > > > > @@ -303,7 +303,8 @@ struct pci_dev *acpi_get_pci_dev(acpi_handle handle) > > > > > > * case pdev->subordinate will be NULL for the parent. > > > > > > */ > > > > > > if (!pbus) { > > > > > > - dev_dbg(&pdev->dev, "Not a PCI-to-PCI bridge\n"); > > > > > > + dev_dbg(&root->device->dev, > > > > > > + "dev %d, function %d is not a PCI-to-PCI bridge\n", dev, fn); > > > > > > > > > > This should use "%02x.%d" to be consistent with the dev_set_name() in > > > > > pci_setup_device(). > > > > > > > > Ah, missed that, will change it and send out a new version tomorrow. > > > > > > I would make the change below (modulo the gmail-induced wthite space > > > breakage), though. > > > > That said -> > > > > > --- > > > drivers/acpi/pci_root.c | 5 +++-- > > > 1 file changed, 3 insertions(+), 2 deletions(-) > > > > > > Index: linux-pm/drivers/acpi/pci_root.c > > > =================================================================== > > > --- linux-pm.orig/drivers/acpi/pci_root.c > > > +++ linux-pm/drivers/acpi/pci_root.c > > > @@ -295,8 +295,6 @@ struct pci_dev *acpi_get_pci_dev(acpi_ha > > > break; > > > > > > pbus = pdev->subordinate; > > > - pci_dev_put(pdev); > > > - > > > /* > > > * This function may be called for a non-PCI device that has a > > > * PCI parent (eg. a disk under a PCI SATA controller). In that > > > @@ -304,9 +302,12 @@ struct pci_dev *acpi_get_pci_dev(acpi_ha > > > */ > > > if (!pbus) { > > > dev_dbg(&pdev->dev, "Not a PCI-to-PCI bridge\n"); > > > + pci_dev_put(pdev); > > > pdev = NULL; > > > break; > > > } > > > + > > > + pci_dev_put(pdev); > > > > -> we are going to use pbus after this and it is pdev->subordinate > > which cannot survive without pdev AFAICS. > > > > Are we not concerned about this case? > > Good point. > > whitehat002, any ideas? You found this issue but it really looks like > it is not anything that can ever be hit, so how far do you want to go to > unwind it? I have an idea, sorry for the delay here. I should be ready to post something tomorrow. Cheers!