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 DE707C6FA86 for ; Sat, 10 Sep 2022 13:33:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229504AbiIJNdV (ORCPT ); Sat, 10 Sep 2022 09:33:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:40024 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229446AbiIJNdU (ORCPT ); Sat, 10 Sep 2022 09:33:20 -0400 Received: from cloudserver094114.home.pl (cloudserver094114.home.pl [79.96.170.134]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DE46A44545; Sat, 10 Sep 2022 06:33:18 -0700 (PDT) Received: from localhost (127.0.0.1) (HELO v370.home.net.pl) by /usr/run/smtp (/usr/run/postfix/private/idea_relay_lmtp) via UNIX with SMTP (IdeaSmtpServer 5.0.0) id d9ff3f23ec2aa29d; Sat, 10 Sep 2022 15:33:17 +0200 Received: from kreacher.localnet (unknown [213.134.169.62]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by v370.home.net.pl (Postfix) with ESMTPSA id 71AC066D496; Sat, 10 Sep 2022 15:33:16 +0200 (CEST) From: "Rafael J. Wysocki" 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 Subject: Re: [PATCH] PCI/ACPI: do not reference a pci device after it has been released Date: Sat, 10 Sep 2022 15:33:15 +0200 Message-ID: <5873315.lOV4Wx5bFT@kreacher> In-Reply-To: References: <20220428142854.1065953-1-gregkh@linuxfoundation.org> <5870387.lOV4Wx5bFT@kreacher> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="UTF-8" X-CLIENT-IP: 213.134.169.62 X-CLIENT-HOSTNAME: 213.134.169.62 X-VADE-SPAMSTATE: clean X-VADE-SPAMCAUSE: gggruggvucftvghtrhhoucdtuddrgedvfedrfedtjedgieekucetufdoteggodetrfdotffvucfrrhhofhhilhgvmecujffqoffgrffnpdggtffipffknecuuegrihhlohhuthemucduhedtnecusecvtfgvtghiphhivghnthhsucdlqddutddtmdenucfjughrpefhvfevufffkfgjfhgggfgtsehtufertddttdejnecuhfhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqnecuggftrfgrthhtvghrnhepfeduudeutdeugfelffduieegiedtueefledvjeegffdttefhhffhtefhleejgfetnecuffhomhgrihhnpehkvghrnhgvlhdrohhrghenucfkphepvddufedrudefgedrudeiledriedvnecuvehluhhsthgvrhfuihiivgeptdenucfrrghrrghmpehinhgvthepvddufedrudefgedrudeiledriedvpdhhvghlohepkhhrvggrtghhvghrrdhlohgtrghlnhgvthdpmhgrihhlfhhrohhmpedftfgrfhgrvghlucflrdcuhgihshhotghkihdfuceorhhjfiesrhhjfiihshhotghkihdrnhgvtheqpdhnsggprhgtphhtthhopeelpdhrtghpthhtohepghhrvghgkhhhsehlihhnuhigfhhouhhnuggrthhiohhnrdhorhhgpdhrtghpthhtoheprhgrfhgrvghlsehkvghrnhgvlhdrohhrghdprhgtphhtthhopehhvghlghgrrghssehkvghrnhgvlhdrohhrghdprhgtphhtthhopegshhgvlhhgrggrshesghhoohhglhgvrdgtohhmpdhrtghpthht oheplhhinhhugidqkhgvrhhnvghlsehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhgvnhgssehkvghrnhgvlhdrohhrghdprhgtphhtthhopehlihhnuhigqdhptghisehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtoheplhhinhhugidqrggtphhisehvghgvrhdrkhgvrhhnvghlrdhorhhgpdhrtghpthhtohephhgrtghkhiiihhdttddvsehgmhgrihhlrdgtohhm X-DCC--Metrics: v370.home.net.pl 1024; Body=9 Fuz1=9 Fuz2=9 Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Saturday, September 10, 2022 7:42:03 AM CEST Greg Kroah-Hartman wrote: > On Fri, Sep 09, 2022 at 11:18:46PM +0200, Rafael J. Wysocki wrote: > > On Friday, September 9, 2022 9:42:53 AM CEST Greg Kroah-Hartman wrote: > > > On Mon, Jun 27, 2022 at 06:37:06PM +0200, Rafael J. Wysocki wrote: > > > > 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. > > > > > > Was this ever posted? > > > > No, it wasn't. Sorry for the glacial pace here. > > > > So the idea is based on the observation that the PCI device returned by the current > > code in acpi_get_pci_dev() needs to be registered, so if it corresponds to an ACPI > > device object, the struct acpi_device representing it must be registered too and, > > moreover, it should be the ACPI companion of that PCI device. Thus it should be > > sufficient to look for it in the ACPI device object's list of physical nodes > > corresponding to it. Hence, the patch below. > > > > I actually can't test it right now (or even compile it for that matter), but > > I'll put it in order tomorrow. > > The idea looks sane to me, let me know if testing works or not, thanks! The patch sent previously had a few build issues, so I've just officially posted a version of it that builds: https://patchwork.kernel.org/project/linux-acpi/patch/2661914.mvXUDI8C0e@kreacher/ To test it, I've applied the appended extra debug patch and checked that the output from it is the same before and after the change above. It is for me. --- drivers/acpi/scan.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+) Index: linux-pm/drivers/acpi/scan.c =================================================================== --- linux-pm.orig/drivers/acpi/scan.c +++ linux-pm/drivers/acpi/scan.c @@ -2537,6 +2537,19 @@ static void __init acpi_get_spcr_uart_ad static bool acpi_scan_initialized; +#include + +static int pci_dev_check(struct device *dev, void *not_used) +{ + struct acpi_device *adev = to_acpi_device(dev); + struct pci_dev *pci_dev = acpi_get_pci_dev(adev->handle); + + if (pci_dev) + dev_info(&adev->dev, "%s: %s\n", __func__, dev_name(&pci_dev->dev)); + + return 0; +} + void __init acpi_scan_init(void) { acpi_status status; @@ -2603,6 +2616,8 @@ void __init acpi_scan_init(void) acpi_scan_initialized = true; + acpi_bus_for_each_dev(pci_dev_check, NULL); + unlock: mutex_unlock(&acpi_scan_lock); }