Re: [Xen-devel] xen/acpi: ACPI memory hotplug

[Dan Carpenter <dan.carpenter@xxxxxxxxxx>]

Hello Liu Jinsong,

This is a semi-automatic email about new static checker warnings.

The patch 259f201cb7ea: "xen/acpi: ACPI memory hotplug" from Jan 24, 
2013, leads to the following Smatch complaint:

drivers/xen/xen-acpi-memhotplug.c:198 acpi_memory_get_device()
         error: we previously assumed 'device' could be null (see line 171)

drivers/xen/xen-acpi-memhotplug.c
   170  
   171          if (!acpi_bus_get_device(handle, &device) && device)
                                                             ^^^^^^
New check.

Btw, checking device is unnecessary.

                if (acpi_bus_get_device(handle, &device) == 0)
                        goto end;

A successful "Get Device" means that "device" is non-NULL; that's built
into the name.  Anyway, if acpi_bus_get_device() fails either something
else will fail or we will Oops in the call to acpi_driver_data().

   172                  goto end;
   173  
   174          status = acpi_get_parent(handle, &phandle);
   175          if (ACPI_FAILURE(status)) {
   176                  pr_warn(PREFIX "Cannot find acpi parent\n");
   177                  return -EINVAL;
   178          }
   179  
   180          /* Get the parent device */
   181          result = acpi_bus_get_device(phandle, &pdevice);
   182          if (result) {
   183                  pr_warn(PREFIX "Cannot get acpi bus device\n");
   184                  return -EINVAL;
   185          }
   186  
   187          /*
   188           * Now add the notified device.  This creates the acpi_device
   189           * and invokes .add function
   190           */
   191          result = acpi_bus_scan(handle);
   192          if (result) {
   193                  pr_warn(PREFIX "Cannot add acpi bus\n");
   194                  return -EINVAL;
   195          }
   196  
   197  end:
   198          *mem_device = acpi_driver_data(device);
                                               ^^^^^^
Dereference.

   199          if (!(*mem_device)) {
   200                  pr_err(PREFIX "Driver data not found\n");

regards,
dan carpenter

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