ACPI: property: Allow _DSD buffer data only for byte accessors

In accordance with ACPI specificication and _DSD data buffer
representation the data there is an array of bytes. Hence,
accessing it with something longer will create a sparse data
which is against of how device property APIs work in general
and also not defined in the ACPI specification (see [1]).
Fix the code to emit an error if non-byte accessor is used to
retrieve _DSD buffer data.

Fixes: 369af6b ("ACPI: property: Read buffer properties as integers")
Link: https://uefi.org/specs/ACPI/6.5/19_ASL_Reference.html#buffer-declare-buffer-object # [1]
Signed-off-by: Andy Shevchenko <[email protected]>
[ rjw: Add missing braces ]
Signed-off-by: Rafael J. Wysocki <[email protected]>

Author: andy-shev

drivers/acpi/property.c

@@ -1102,25 +1102,26 @@ static int acpi_data_prop_read(const struct acpi_device_data *data,
 	switch (proptype) {
 	case DEV_PROP_STRING:
 		break;
-	case DEV_PROP_U8 ... DEV_PROP_U64:
+	default:
 		if (obj->type == ACPI_TYPE_BUFFER) {
 			if (nval > obj->buffer.length)
 				return -EOVERFLOW;
-			break;
+		} else {
+			if (nval > obj->package.count)
+				return -EOVERFLOW;
 		}
-		fallthrough;
-	default:
-		if (nval > obj->package.count)
-			return -EOVERFLOW;
 		break;
 	}
 	if (nval == 0)
 		return -EINVAL;
 
-	if (obj->type != ACPI_TYPE_BUFFER)
-		items = obj->package.elements;
-	else
+	if (obj->type == ACPI_TYPE_BUFFER) {
+		if (proptype != DEV_PROP_U8)
+			return -EPROTO;
 		items = obj;
+	} else {
+		items = obj->package.elements;
+	}
 
 	switch (proptype) {
 	case DEV_PROP_U8: