On Mon, Dec 2, 2013 at 6:49 AM, Rafael J. Wysocki <r...@rjwysocki.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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