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: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Tested-by: Mika Westerberg <mika.westerberg@linux.intel.com>
diff --git a/drivers/acpi/bus.c b/drivers/acpi/bus.c
index fcb59c2..c323777 100644
--- a/drivers/acpi/bus.c
+++ b/drivers/acpi/bus.c
@@ -340,7 +340,7 @@
*/
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 @@
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);
}
}