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

[ Upstream commit 98e26302 ]

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: ff0e9f26 ("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: Sasha Levin <sashal@kernel.org>

drivers/platform/x86/alienware-wmi.c

@@ -522,23 +522,22 @@ 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, 0,
 					     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, 0,
 					     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;
-
 }
 
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