ACPI / fan: avoid null pointer deference error

Fix a null pointer deference by acpi_driver_data() if device is
null.  We should only set cdev and check this is OK after we are
sure device is not null.

Smatch analysis:

drivers/acpi/fan.c:179 acpi_fan_remove() warn: variable dereferenced
  before check 'device' (see line 177)

Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

1 files changed, 6 insertions, 2 deletions

diff --git a/drivers/acpi/fan.c b/drivers/acpi/fan.c
index f815da82c765..8d1c0105e113 100644
--- a/drivers/acpi/fan.c
+++ b/drivers/acpi/fan.c
@@ -174,9 +174,13 @@ static int acpi_fan_add(struct acpi_device *device)
 
 static int acpi_fan_remove(struct acpi_device *device)
 {
-        struct thermal_cooling_device *cdev = acpi_driver_data(device);
+        struct thermal_cooling_device *cdev;
+
+        if (!device)
+                return -EINVAL;
 
-        if (!device || !cdev)
+        cdev =  acpi_driver_data(device);
+        if (!cdev)
                 return -EINVAL;
 
         sysfs_remove_link(&device->dev.kobj, "thermal_cooling");