linux-kernel - Re: [PATCH v2 04/10] PCI: Destroy pci dev only once

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Message-ID: <CAE9FiQV1KvpzfTmzbERS8heAE1z5zf=CjXnnjS9ZMBqmhY7rkw@mail.gmail.com>
Date:	Thu, 5 Dec 2013 22:52:36 -0800
From:	Yinghai Lu <yinghai@...nel.org>
To:	"Rafael J. Wysocki" <rjw@...ysocki.net>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Gu Zheng <guz.fnst@...fujitsu.com>,
	Guo Chao <yan@...ux.vnet.ibm.com>,
	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Mika Westerberg <mika.westerberg@...ux.intel.com>,
	Myron Stowe <myron.stowe@...il.com>
Subject: Re: [PATCH v2 04/10] PCI: Destroy pci dev only once

On Mon, Dec 2, 2013 at 6:49 AM, Rafael J. Wysocki <rjw@...ysocki.net> wrote:
>
> Scenario 5: pci_stop_and_remove_bus_device() is run concurrently
>   for a device and its parent bridge via remove_callback().
>
>   In that case both code paths attempt to acquire
>   pci_remove_rescan_mutex.  If the child device removal acquires
>   it first, there will be no problems.  However, if the parent
>   bridge removal acquires it first, it will eventually execute
>   pci_destroy_dev() for the child device, but that device will
>   not be freed yet due to the reference held by the concurrent
>   child removal.  Consequently, both pci_stop_bus_device() and
>   pci_remove_bus_device() will be executed for that device
>   unnecessarily and pci_destroy_dev() will see a corrupted list
>   head in that object.  Moreover, an excess put_device() will
>   be executed for that device in that case which may lead to a
>   use-after-free in the final kobject_put() done by
>   sysfs_schedule_callback_work().
>
> Index: linux-pm/include/linux/pci.h
> ===================================================================
> --- linux-pm.orig/include/linux/pci.h
> +++ linux-pm/include/linux/pci.h
> @@ -321,6 +321,7 @@ struct pci_dev {
>         unsigned int    multifunction:1;/* Part of multi-function device */
>         /* keep track of device state */
>         unsigned int    is_added:1;
> +       unsigned int    is_gone:1;
>         unsigned int    is_busmaster:1; /* device is busmaster */
>         unsigned int    no_msi:1;       /* device may not use msi */
>         unsigned int    block_cfg_access:1;     /* config space access is blocked */
> Index: linux-pm/drivers/pci/remove.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/remove.c
> +++ linux-pm/drivers/pci/remove.c
> @@ -34,6 +34,7 @@ static void pci_stop_dev(struct pci_dev
>
>  static void pci_destroy_dev(struct pci_dev *dev)
>  {
> +       dev->is_gone = 1;
>         device_del(&dev->dev);
>
>         down_write(&pci_bus_sem);
> @@ -109,8 +110,10 @@ static void pci_remove_bus_device(struct
>   */
>  void pci_stop_and_remove_bus_device(struct pci_dev *dev)
>  {
> -       pci_stop_bus_device(dev);
> -       pci_remove_bus_device(dev);
> +       if (!dev->is_gone) {
> +               pci_stop_bus_device(dev);
> +               pci_remove_bus_device(dev);
> +       }
>  }
>  EXPORT_SYMBOL(pci_stop_and_remove_bus_device);
>

Yes, above change should address sys double remove problem.

Thanks

Yinghai
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