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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,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 5F838C433DF for ; Thu, 14 May 2020 10:30:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 4204420760 for ; Thu, 14 May 2020 10:30:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726200AbgENKag (ORCPT ); Thu, 14 May 2020 06:30:36 -0400 Received: from foss.arm.com ([217.140.110.172]:33884 "EHLO foss.arm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725978AbgENKad (ORCPT ); Thu, 14 May 2020 06:30:33 -0400 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 5C93D31B; Thu, 14 May 2020 03:30:32 -0700 (PDT) Received: from red-moon.cambridge.arm.com (unknown [10.57.1.235]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 80A3E3F305; Thu, 14 May 2020 03:30:31 -0700 (PDT) Date: Thu, 14 May 2020 11:30:28 +0100 From: Lorenzo Pieralisi To: Rob Herring Cc: Bjorn Helgaas , linux-pci@vger.kernel.org, Anders Roxell , Arnd Bergmann Subject: Re: [PATCH 2/2] PCI: Fix pci_host_bridge struct device release/free handling Message-ID: <20200514103028.GA16121@red-moon.cambridge.arm.com> References: <20200513223859.11295-1-robh@kernel.org> <20200513223859.11295-2-robh@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200513223859.11295-2-robh@kernel.org> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Wed, May 13, 2020 at 05:38:59PM -0500, Rob Herring wrote: > The PCI code has several paths where the struct pci_host_bridge is freed > directly. This is wrong because it contains a struct device which is > refcounted and should be freed using put_device(). This can result in > use-after-free errors. I think this problem has existed since 2012 with > commit 7b5436635800 ("PCI: add generic device into pci_host_bridge > struct"). It generally hasn't mattered as most host bridge drivers are > still built-in and can't unbind. > > The problem is a struct device should never be freed directly once > device_initialize() is called and a ref is held, but that doesn't happen > until pci_register_host_bridge(). There's then a window between > allocating the host bridge and pci_register_host_bridge() where kfree > should be used. This is fragile and requires callers to do the right > thing. To fix this, we need to split device_register() into > device_initialize() and device_add() calls, so that the host bridge > struct is always freed by using a put_device(). > > devm_pci_alloc_host_bridge() is using devm_kzalloc() to allocate struct > pci_host_bridge which will be freed directly. Instead, we can use a > custom devres action to call put_device(). > > Reported-by: Anders Roxell > Cc: Arnd Bergmann > Cc: Bjorn Helgaas > Signed-off-by: Rob Herring > --- > drivers/pci/probe.c | 36 +++++++++++++++++++----------------- > drivers/pci/remove.c | 2 +- > 2 files changed, 20 insertions(+), 18 deletions(-) > > diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c > index e21dc71b1907..e064ded6fbec 100644 > --- a/drivers/pci/probe.c > +++ b/drivers/pci/probe.c > @@ -565,7 +565,7 @@ static struct pci_bus *pci_alloc_bus(struct pci_bus *parent) > return b; > } > > -static void devm_pci_release_host_bridge_dev(struct device *dev) > +static void pci_release_host_bridge_dev(struct device *dev) > { > struct pci_host_bridge *bridge = to_pci_host_bridge(dev); > > @@ -574,12 +574,7 @@ static void devm_pci_release_host_bridge_dev(struct device *dev) > > pci_free_resource_list(&bridge->windows); > pci_free_resource_list(&bridge->dma_ranges); > -} > - > -static void pci_release_host_bridge_dev(struct device *dev) > -{ > - devm_pci_release_host_bridge_dev(dev); > - kfree(to_pci_host_bridge(dev)); > + kfree(bridge); > } > > static void pci_init_host_bridge(struct pci_host_bridge *bridge) > @@ -599,6 +594,8 @@ static void pci_init_host_bridge(struct pci_host_bridge *bridge) > bridge->native_pme = 1; > bridge->native_ltr = 1; > bridge->native_dpc = 1; > + > + device_initialize(&bridge->dev); > } > > struct pci_host_bridge *pci_alloc_host_bridge(size_t priv) > @@ -616,17 +613,25 @@ struct pci_host_bridge *pci_alloc_host_bridge(size_t priv) > } > EXPORT_SYMBOL(pci_alloc_host_bridge); > > +static void devm_pci_alloc_host_bridge_release(void *data) > +{ > + pci_free_host_bridge(data); > +} > + > struct pci_host_bridge *devm_pci_alloc_host_bridge(struct device *dev, > size_t priv) > { > + int ret; > struct pci_host_bridge *bridge; > > - bridge = devm_kzalloc(dev, sizeof(*bridge) + priv, GFP_KERNEL); > + bridge = pci_alloc_host_bridge(priv); > if (!bridge) > return NULL; > > - pci_init_host_bridge(bridge); > - bridge->dev.release = devm_pci_release_host_bridge_dev; > + ret = devm_add_action_or_reset(dev, devm_pci_alloc_host_bridge_release, > + bridge); > + if (ret) > + return NULL; > > return bridge; > } > @@ -634,10 +639,7 @@ EXPORT_SYMBOL(devm_pci_alloc_host_bridge); > > void pci_free_host_bridge(struct pci_host_bridge *bridge) > { > - pci_free_resource_list(&bridge->windows); > - pci_free_resource_list(&bridge->dma_ranges); > - > - kfree(bridge); > + put_device(&bridge->dev); > } > EXPORT_SYMBOL(pci_free_host_bridge); > > @@ -908,7 +910,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > if (err) > goto free; > > - err = device_register(&bridge->dev); > + err = device_add(&bridge->dev); > if (err) { > put_device(&bridge->dev); > goto free; > @@ -978,7 +980,7 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge) > > unregister: > put_device(&bridge->dev); > - device_unregister(&bridge->dev); > + device_del(&bridge->dev); I think we need to execute device_del() first, then put_device(). Thank you for fixing this code path. Lorenzo > free: > kfree(bus); > @@ -2953,7 +2955,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus, > return bridge->bus; > > err_out: > - kfree(bridge); > + put_device(&bridge->dev); > return NULL; > } > EXPORT_SYMBOL_GPL(pci_create_root_bus); > diff --git a/drivers/pci/remove.c b/drivers/pci/remove.c > index e9c6b120cf45..95dec03d9f2a 100644 > --- a/drivers/pci/remove.c > +++ b/drivers/pci/remove.c > @@ -160,6 +160,6 @@ void pci_remove_root_bus(struct pci_bus *bus) > host_bridge->bus = NULL; > > /* remove the host bridge */ > - device_unregister(&host_bridge->dev); > + device_del(&host_bridge->dev); > } > EXPORT_SYMBOL_GPL(pci_remove_root_bus); > -- > 2.20.1 >