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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/platform/x86/alienware-wmi.c b/drivers/platform/x86/alienware-wmi.c
index bee2115ecf10145edaf47638f9a6abc30b07d0dc..ec7482c7e7eb6ef1904101ea0bc61259555b8633 100644 (file)
--- a/drivers/platform/x86/alienware-wmi.c
+++ b/drivers/platform/x86/alienware-wmi.c
@@ -504,23 +504,22 @@ static acpi_status alienware_wmax_command(struct wmax_basic_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;
-
 }
 
 /*