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/scan.c b/drivers/acpi/scan.c
index 7384158..59eba29 100644
--- a/drivers/acpi/scan.c
+++ b/drivers/acpi/scan.c
@@ -476,7 +476,7 @@
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 @@
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 @@
/* 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 @@
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 @@
}
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 *))
{
