xen/acpi: xen memory hotplug minor updates

Dan Carpenter found current xen memory hotplug logic
has potential issue: at func acpi_memory_get_device()
*mem_device = acpi_driver_data(device);
while the device may be NULL and then dereference.

At native side, Rafael recently updated acpi_memory_get_device(),
dropping acpi_bus_add, adding lock, and avoiding above issue.

This patch updates xen memory hotplug logic accordingly, removing
redundant logic, adding lock, and avoiding dereference.

Signed-off-by: Liu Jinsong <jinsong.liu@intel.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

diff --git a/drivers/xen/xen-acpi-memhotplug.c b/drivers/xen/xen-acpi-memhotplug.c
index 853b12d..faef5b3 100644 (file)
--- a/drivers/xen/xen-acpi-memhotplug.c
+++ b/drivers/xen/xen-acpi-memhotplug.c
@@ -158,31 +158,17 @@ acpi_memory_get_device_resources(struct acpi_memory_device *mem_device)
        return 0;
 }
 
-static int
-acpi_memory_get_device(acpi_handle handle,
-                      struct acpi_memory_device **mem_device)
+static int acpi_memory_get_device(acpi_handle handle,
+                                 struct acpi_memory_device **mem_device)
 {
-       acpi_status status;
-       acpi_handle phandle;
        struct acpi_device *device = NULL;
-       struct acpi_device *pdevice = NULL;
-       int result;
+       int result = 0;
 
-       if (!acpi_bus_get_device(handle, &device) && device)
-               goto end;
+       acpi_scan_lock_acquire();
 
-       status = acpi_get_parent(handle, &phandle);
-       if (ACPI_FAILURE(status)) {
-               pr_warn(PREFIX "Cannot find acpi parent\n");
-               return -EINVAL;
-       }
-
-       /* Get the parent device */
-       result = acpi_bus_get_device(phandle, &pdevice);
-       if (result) {
-               pr_warn(PREFIX "Cannot get acpi bus device\n");
-               return -EINVAL;
-       }
+       acpi_bus_get_device(handle, &device);
+       if (device)
+               goto end;
 
        /*
         * Now add the notified device.  This creates the acpi_device
@@ -190,18 +176,28 @@ acpi_memory_get_device(acpi_handle handle,
         */
        result = acpi_bus_scan(handle);
        if (result) {
-               pr_warn(PREFIX "Cannot add acpi bus\n");
-               return -EINVAL;
+               pr_warn(PREFIX "ACPI namespace scan failed\n");
+               result = -EINVAL;
+               goto out;
+       }
+       result = acpi_bus_get_device(handle, &device);
+       if (result) {
+               pr_warn(PREFIX "Missing device object\n");
+               result = -EINVAL;
+               goto out;
        }
 
 end:
        *mem_device = acpi_driver_data(device);
        if (!(*mem_device)) {
-               pr_err(PREFIX "Driver data not found\n");
-               return -ENODEV;
+               pr_err(PREFIX "driver data not found\n");
+               result = -ENODEV;
+               goto out;
        }
 
-       return 0;
+out:
+       acpi_scan_lock_release();
+       return result;
 }
 
 static int acpi_memory_check_device(struct acpi_memory_device *mem_device)
@@ -259,12 +255,15 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
                ACPI_DEBUG_PRINT((ACPI_DB_INFO,
                        "\nReceived EJECT REQUEST notification for device\n"));
 
+               acpi_scan_lock_acquire();
                if (acpi_bus_get_device(handle, &device)) {
+                       acpi_scan_lock_release();
                        pr_err(PREFIX "Device doesn't exist\n");
                        break;
                }
                mem_device = acpi_driver_data(device);
                if (!mem_device) {
+                       acpi_scan_lock_release();
                        pr_err(PREFIX "Driver Data is NULL\n");
                        break;
                }
@@ -274,6 +273,7 @@ static void acpi_memory_device_notify(acpi_handle handle, u32 event, void *data)
                 * acpi_bus_remove if Xen support hotremove in the future
                 */
                acpi_memory_disable_device(mem_device);
+               acpi_scan_lock_release();
                break;
 
        default: