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ACPI / hotplug: Fix potential race in acpi_bus_notify()

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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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
This commit is contained in:
Rafael J. Wysocki 2014-02-04 00:43:05 +01:00
parent 7c2e17714e
commit 78ea4639a7
3 changed files with 40 additions and 10 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

6
drivers/acpi/bus.c
View file

@ -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);
}
}

42
drivers/acpi/scan.c
View file

@ -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 *))
{

2
include/acpi/acpi_bus.h
View file

@ -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);