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

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Saturday, November 30, 2013 01:31:33 AM Rafael J. Wysocki wrote:
> On Saturday, November 30, 2013 12:45:55 AM Rafael J. Wysocki wrote:
> > On Saturday, November 30, 2013 12:38:26 AM Rafael J. Wysocki wrote:
> > > On Tuesday, November 26, 2013 06:26:54 PM Yinghai Lu wrote:
> > > > On Tue, Nov 26, 2013 at 5:24 PM, Rafael J. Wysocki <rjw@xxxxxxxxxxxxx> wrote:
> > > > >
> > > > > So assume pci_destroy_dev() is called twice in parallel for the same dev
> > > > > by two different threads.  Thread 1 does the atomic_inc_and_test() and
> > > > > finds that it is OK to do the device_del() and put_device() which causes
> > > > > the device object to be freed.  Then thread 2 does the atomic_inc_and_test()
> > > > > on the already freed device object and crashes the kernel.
> > > > >
> > > > thread2 should still hold one extra reference.
> > > > that is in
> > > >   device_schedule_callback
> > > >      ==> sysfs_schedule_callback
> > > >          ==> kobject_get(kobj)
> > > > 
> > > > pci_destroy_dev for thread2 is called at this point.
> > > > 
> > > > and that reference will be released from
> > > >         sysfs_schedule_callback
> > > >         ==> kobject_put()...
> > > 
> > > Well, that would be the case if thread 2 was started by device_schedule_callback(),
> > > but again, for example, it may be trim_stale_devices() started by acpiphp_check_bridge()
> > > that doesn't hold extra references to the pci_dev.  [Well, that piece of code
> > > is racy anyway, because it walks bus->devices without locking.  Which is my
> > > fault too, because I overlooked that.  Shame, shame.]
> > > 
> > > Perhaps we can do something like the (untested) patch below (in addition to the
> > > $subject patch).  Do you see any immediate problems with it?
> > 
> > Ah, I see one.  It will break pci_stop_bus_device() and pci_remove_bus_device().
> > So much for being clever.
> > 
> > Moreover, it looks like those two routines above are racy too for the same
> > reason?
> 
> The (still untested) patch below is what I have come up with for now.  The
> is_gone flag is now only operated under pci_remove_rescan_mutex, so it need
> not be atomic.  Of course, whoever calls pci_stop_and_remove_bus_device()
> (the "locked" one) should hold a ref to the device being removed to avoid
> use-after-free (the callers need to be audited for that).
> 
> Well, I probably still missed something, because it's the middle of the night
> and I should be going to sleep instead of starig at the PCI removal code.  Sigh.

Thunderbolt hotplug works for me with this patch applied FWIW.

> ---
>  drivers/pci/hotplug/acpiphp_glue.c |   15 ++++++++++++---
>  drivers/pci/pci-sysfs.c            |   17 ++++++++++++-----
>  drivers/pci/pci.h                  |    3 +++
>  drivers/pci/remove.c               |   15 +++++++++++++--
>  include/linux/pci.h                |    1 +
>  5 files changed, 41 insertions(+), 10 deletions(-)
> 
> Index: linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/hotplug/acpiphp_glue.c
> +++ linux-pm/drivers/pci/hotplug/acpiphp_glue.c
> @@ -553,6 +553,8 @@ static void __ref enable_slot(struct acp
>  	int max, pass;
>  	LIST_HEAD(add_list);
>  
> +	lock_pci_remove_rescan();
> +
>  	acpiphp_rescan_slot(slot);
>  	max = acpiphp_max_busnr(bus);
>  	for (pass = 0; pass < 2; pass++) {
> @@ -586,6 +588,8 @@ static void __ref enable_slot(struct acp
>  
>  	pci_bus_add_devices(bus);
>  
> +	unlock_pci_remove_rescan();
> +
>  	slot->flags |= SLOT_ENABLED;
>  	list_for_each_entry(func, &slot->funcs, sibling) {
>  		dev = pci_get_slot(bus, PCI_DEVFN(slot->device,
> @@ -626,6 +630,7 @@ static void disable_slot(struct acpiphp_
>  	struct acpiphp_func *func;
>  	struct pci_dev *pdev;
>  
> +	lock_pci_remove_rescan();
>  	/*
>  	 * enable_slot() enumerates all functions in this device via
>  	 * pci_scan_slot(), whether they have associated ACPI hotplug
> @@ -633,9 +638,10 @@ static void disable_slot(struct acpiphp_
>  	 * here.
>  	 */
>  	while ((pdev = dev_in_slot(slot))) {
> -		pci_stop_and_remove_bus_device(pdev);
> +		__pci_stop_and_remove_bus_device(pdev);
>  		pci_dev_put(pdev);
>  	}
> +	unlock_pci_remove_rescan();
>  
>  	list_for_each_entry(func, &slot->funcs, sibling)
>  		acpiphp_bus_trim(func_to_handle(func));
> @@ -710,7 +716,7 @@ static void trim_stale_devices(struct pc
>  		alive = pci_bus_read_dev_vendor_id(dev->bus, dev->devfn, &v, 0);
>  	}
>  	if (!alive) {
> -		pci_stop_and_remove_bus_device(dev);
> +		__pci_stop_and_remove_bus_device(dev);
>  		if (handle)
>  			acpiphp_bus_trim(handle);
>  	} else if (bus) {
> @@ -743,12 +749,15 @@ static void acpiphp_check_bridge(struct
>  		mutex_lock(&slot->crit_sect);
>  		/* wake up all functions */
>  		if (get_slot_status(slot) == ACPI_STA_ALL) {
> +			lock_pci_remove_rescan();
> +
>  			/* remove stale devices if any */
>  			list_for_each_entry_safe(dev, tmp, &bus->devices,
>  						 bus_list)
>  				if (PCI_SLOT(dev->devfn) == slot->device)
>  					trim_stale_devices(dev);
>  
> +			unlock_pci_remove_rescan();
>  			/* configure all functions */
>  			enable_slot(slot);
>  		} else {
> @@ -783,7 +792,7 @@ static void acpiphp_sanitize_bus(struct
>  					res->end) {
>  				/* Could not assign a required resources
>  				 * for this device, remove it */
> -				pci_stop_and_remove_bus_device(dev);
> +				__pci_stop_and_remove_bus_device(dev);
>  				break;
>  			}
>  		}
> Index: linux-pm/drivers/pci/pci-sysfs.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci-sysfs.c
> +++ linux-pm/drivers/pci/pci-sysfs.c
> @@ -298,6 +298,17 @@ msi_bus_store(struct device *dev, struct
>  static DEVICE_ATTR_RW(msi_bus);
>  
>  static DEFINE_MUTEX(pci_remove_rescan_mutex);
> +
> +void lock_pci_remove_rescan(void)
> +{
> +	mutex_lock(&pci_remove_rescan_mutex);
> +}
> +
> +void unlock_pci_remove_rescan(void)
> +{
> +	mutex_unlock(&pci_remove_rescan_mutex);
> +}
> +
>  static ssize_t bus_rescan_store(struct bus_type *bus, const char *buf,
>  				size_t count)
>  {
> @@ -354,11 +365,7 @@ static struct device_attribute dev_resca
>  
>  static void remove_callback(struct device *dev)
>  {
> -	struct pci_dev *pdev = to_pci_dev(dev);
> -
> -	mutex_lock(&pci_remove_rescan_mutex);
> -	pci_stop_and_remove_bus_device(pdev);
> -	mutex_unlock(&pci_remove_rescan_mutex);
> +	pci_stop_and_remove_bus_device(to_pci_dev(dev));
>  }
>  
>  static ssize_t
> Index: linux-pm/drivers/pci/pci.h
> ===================================================================
> --- linux-pm.orig/drivers/pci/pci.h
> +++ linux-pm/drivers/pci/pci.h
> @@ -11,8 +11,11 @@ extern const unsigned char pcie_link_spe
>  
>  /* Functions internal to the PCI core code */
>  
> +void lock_pci_remove_rescan(void);
> +void unlock_pci_remove_rescan(void);
>  int pci_create_sysfs_dev_files(struct pci_dev *pdev);
>  void pci_remove_sysfs_dev_files(struct pci_dev *pdev);
> +void __pci_stop_and_remove_bus_device(struct pci_dev *pdev);
>  #if !defined(CONFIG_DMI) && !defined(CONFIG_ACPI)
>  static inline void pci_create_firmware_label_files(struct pci_dev *pdev)
>  { return; }
> Index: linux-pm/drivers/pci/remove.c
> ===================================================================
> --- linux-pm.orig/drivers/pci/remove.c
> +++ linux-pm/drivers/pci/remove.c
> @@ -34,6 +34,10 @@ static void pci_stop_dev(struct pci_dev
>  
>  static void pci_destroy_dev(struct pci_dev *dev)
>  {
> +	if (dev->is_gone)
> +		return;
> +
> +	dev->is_gone = 1;
>  	device_del(&dev->dev);
>  
>  	down_write(&pci_bus_sem);
> @@ -95,6 +99,12 @@ static void pci_remove_bus_device(struct
>  	pci_destroy_dev(dev);
>  }
>  
> +void __pci_stop_and_remove_bus_device(struct pci_dev *dev)
> +{
> +	pci_stop_bus_device(dev);
> +	pci_remove_bus_device(dev);
> +}
> +
>  /**
>   * pci_stop_and_remove_bus_device - remove a PCI device and any children
>   * @dev: the device to remove
> @@ -109,8 +119,9 @@ 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);
> +	lock_pci_remove_rescan();
> +	__pci_stop_and_remove_bus_device(dev);
> +	unlock_pci_remove_rescan();
>  }
>  EXPORT_SYMBOL(pci_stop_and_remove_bus_device);
>  
> 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 */
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-pci" in
> the body of a message to majordomo@xxxxxxxxxxxxxxx
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
--
To unsubscribe from this list: send the line "unsubscribe linux-pci" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html




[Index of Archives]     [DMA Engine]     [Linux Coverity]     [Linux USB]     [Video for Linux]     [Linux Audio Users]     [Yosemite News]     [Linux Kernel]     [Linux SCSI]     [Greybus]

  Powered by Linux