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Commit 78ea4639 authored by Rafael J. Wysocki's avatar Rafael J. Wysocki
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ACPI / hotplug: Fix potential race in acpi_bus_notify() 



There is a slight possibility for the ACPI device object pointed to
by adev in acpi_hotplug_notify_cb() to become invalid between the
acpi_bus_get_device() that it comes from and the subsequent dereference
of that pointer under get_device().  Namely, if acpi_scan_drop_device()
runs in parallel with acpi_hotplug_notify_cb(), acpi_device_del_work_fn()
queued up by it may delete the device object in question right after
a successful execution of acpi_bus_get_device() in acpi_bus_notify().

An analogous problem is present in acpi_bus_notify() where the device
pointer coming from acpi_bus_get_device() may become invalid before
it subsequent dereference in the "if" block.

To prevent that from happening, introduce a new function,
acpi_bus_get_acpi_device(), working analogously to acpi_bus_get_device()
except that it will grab a reference to the ACPI device object returned
by it and it will do that under the ACPICA's namespace mutex.  Then,
make both acpi_hotplug_notify_cb() and acpi_bus_notify() use
acpi_bus_get_acpi_device() instead of acpi_bus_get_device() so as to
ensure that the pointers used by them will not become stale at one
point.

In addition to that, introduce acpi_bus_put_acpi_device() as a wrapper
around put_device() to be used along with acpi_bus_get_acpi_device()
and make the (new) users of the latter use acpi_bus_put_acpi_device()
too.

Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: default avatarMika Westerberg <mika.westerberg@linux.intel.com>
parent 7c2e1771

drivers/acpi/bus.c

+4 −2
Original line number Diff line number Diff line
@@ -340,7 +340,7 @@ static void acpi_bus_osc_support(void) 
 */

static void acpi_bus_notify(acpi_handle handle, u32 type, void *data)

{

	struct acpi_device *device = NULL;

	struct acpi_device *device;

	struct acpi_driver *driver;



	ACPI_DEBUG_PRINT((ACPI_DB_INFO, "Notification %#02x to handle %p\n",
@@ -387,12 +387,14 @@ static void acpi_bus_notify(acpi_handle handle, u32 type, void *data) 
		break;

	}



	acpi_bus_get_device(handle, &device);

	device = acpi_bus_get_acpi_device(handle);

	if (device) {

		driver = device->driver;

		if (driver && driver->ops.notify &&

		    (driver->flags & ACPI_DRIVER_ALL_NOTIFY_EVENTS))

			driver->ops.notify(device, type);



		acpi_bus_put_acpi_device(device);

	}

}

drivers/acpi/scan.c

+34 −8
Original line number Diff line number Diff line
@@ -476,7 +476,7 @@ static void acpi_device_hotplug(void *data, u32 src) 


 out:

	acpi_evaluate_hotplug_ost(adev->handle, src, ost_code, NULL);

	put_device(&adev->dev);

	acpi_bus_put_acpi_device(adev);

	mutex_unlock(&acpi_scan_lock);

	unlock_device_hotplug();

}
@@ -488,9 +488,6 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data) 
	struct acpi_device *adev;

	acpi_status status;



	if (acpi_bus_get_device(handle, &adev))

		goto err_out;



	switch (type) {

	case ACPI_NOTIFY_BUS_CHECK:

		acpi_handle_debug(handle, "ACPI_NOTIFY_BUS_CHECK event\n");
@@ -512,12 +509,15 @@ static void acpi_hotplug_notify_cb(acpi_handle handle, u32 type, void *data) 
		/* non-hotplug event; possibly handled by other handler */

		return;

	}

	get_device(&adev->dev);

	adev = acpi_bus_get_acpi_device(handle);

	if (!adev)

		goto err_out;



	status = acpi_hotplug_execute(acpi_device_hotplug, adev, type);

	if (ACPI_SUCCESS(status))

		return;



	put_device(&adev->dev);

	acpi_bus_put_acpi_device(adev);



 err_out:

	acpi_evaluate_hotplug_ost(handle, type, ost_code, NULL);
@@ -1112,14 +1112,16 @@ static void acpi_scan_drop_device(acpi_handle handle, void *context) 
	mutex_unlock(&acpi_device_del_lock);

}



int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device)

static int acpi_get_device_data(acpi_handle handle, struct acpi_device **device,

				void (*callback)(void *))

{

	acpi_status status;



	if (!device)

		return -EINVAL;



	status = acpi_get_data(handle, acpi_scan_drop_device, (void **)device);

	status = acpi_get_data_full(handle, acpi_scan_drop_device,

				    (void **)device, callback);

	if (ACPI_FAILURE(status) || !*device) {

		ACPI_DEBUG_PRINT((ACPI_DB_INFO, "No context for object [%p]\n",

				  handle));
@@ -1127,8 +1129,32 @@ int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device) 
	}

	return 0;

}



int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device)

{

	return acpi_get_device_data(handle, device, NULL);

}

EXPORT_SYMBOL(acpi_bus_get_device);



static void get_acpi_device(void *dev)

{

	if (dev)

		get_device(&((struct acpi_device *)dev)->dev);

}



struct acpi_device *acpi_bus_get_acpi_device(acpi_handle handle)

{

	struct acpi_device *adev = NULL;



	acpi_get_device_data(handle, &adev, get_acpi_device);

	return adev;

}



void acpi_bus_put_acpi_device(struct acpi_device *adev)

{

	put_device(&adev->dev);

}



int acpi_device_add(struct acpi_device *device,

		    void (*release)(struct device *))

{

include/acpi/acpi_bus.h

+2 −0
Original line number Diff line number Diff line
@@ -381,6 +381,8 @@ extern int unregister_acpi_notifier(struct notifier_block *); 
 */



int acpi_bus_get_device(acpi_handle handle, struct acpi_device **device);

struct acpi_device *acpi_bus_get_acpi_device(acpi_handle handle);

void acpi_bus_put_acpi_device(struct acpi_device *adev);

acpi_status acpi_bus_get_status_handle(acpi_handle handle,

				       unsigned long long *sta);

int acpi_bus_get_status(struct acpi_device *device);