platform/x86: alienware-wmi: fix kfree on potentially uninitialized pointer

commit 98e2630284ab741804bd0713e932e725466f2f84 upstream.

Currently the kfree of output.pointer can be potentially freeing
an uninitalized pointer in the case where out_data is NULL. Fix this
by reworking the case where out_data is not-null to perform the
ACPI status check and also the kfree of outpoint.pointer in one block
and hence ensuring the pointer is only freed when it has been used.

Also replace the if (ptr != NULL) idiom with just if (ptr).

Fixes: ff0e9f26288d ("platform/x86: alienware-wmi: Correct a memory leak")
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Darren Hart (VMware) <dvhart@infradead.org>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>

diff --git a/drivers/platform/x86/alienware-wmi.c b/drivers/platform/x86/alienware-wmi.c
index 2899727069e6d4a1c42075bc6dc47242ec815dfb..eae2dcb209c65b7d20d20a9c1cda0e59dbc56253 100644 (file)
--- a/drivers/platform/x86/alienware-wmi.c
+++ b/drivers/platform/x86/alienware-wmi.c
@@ -433,23 +433,22 @@ static acpi_status alienware_hdmi_command(struct hdmi_args *in_args,
 
        input.length = (acpi_size) sizeof(*in_args);
        input.pointer = in_args;
-       if (out_data != NULL) {
+       if (out_data) {
                output.length = ACPI_ALLOCATE_BUFFER;
                output.pointer = NULL;
                status = wmi_evaluate_method(WMAX_CONTROL_GUID, 1,
                                             command, &input, &output);
-       } else
+               if (ACPI_SUCCESS(status)) {
+                       obj = (union acpi_object *)output.pointer;
+                       if (obj && obj->type == ACPI_TYPE_INTEGER)
+                               *out_data = (u32)obj->integer.value;
+               }
+               kfree(output.pointer);
+       } else {
                status = wmi_evaluate_method(WMAX_CONTROL_GUID, 1,
                                             command, &input, NULL);
-
-       if (ACPI_SUCCESS(status) && out_data != NULL) {
-               obj = (union acpi_object *)output.pointer;
-               if (obj && obj->type == ACPI_TYPE_INTEGER)
-                       *out_data = (u32) obj->integer.value;
        }
-       kfree(output.pointer);
        return status;
-
 }
 
 static ssize_t show_hdmi_cable(struct device *dev,