HID: core: do not upper bound the collection stack

Looks like 4 was sufficient until now. However, the Surface Dial needs
a stack of 5 and simply fails at probing.
Dynamically add HID_COLLECTION_STACK_SIZE to the size of the stack if
we hit the upper bound.

Checkpatch complains about bare unsigned, so converting those to
'unsigned int' in struct hid_parser

Acked-by: Peter Hutterer <peter.hutterer@who-t.net>
Signed-off-by: Benjamin Tissoires <benjamin.tissoires@redhat.com>
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-core.c

@@ -128,9 +128,19 @@ static int open_collection(struct hid_parser *parser, unsigned type)
 
 	usage = parser->local.usage[0];
 
-	if (parser->collection_stack_ptr == HID_COLLECTION_STACK_SIZE) {
-		hid_err(parser->device, "collection stack overflow\n");
-		return -EINVAL;
+	if (parser->collection_stack_ptr == parser->collection_stack_size) {
+		unsigned int *collection_stack;
+		unsigned int new_size = parser->collection_stack_size +
+					HID_COLLECTION_STACK_SIZE;
+
+		collection_stack = krealloc(parser->collection_stack,
+					    new_size * sizeof(unsigned int),
+					    GFP_KERNEL);
+		if (!collection_stack)
+			return -ENOMEM;
+
+		parser->collection_stack = collection_stack;
+		parser->collection_stack_size = new_size;
 	}
 
 	if (parser->device->maxcollection == parser->device->collection_size) {
@@ -840,6 +850,7 @@ static int hid_scan_report(struct hid_device *hid)
 		break;
 	}
 
+	kfree(parser->collection_stack);
 	vfree(parser);
 	return 0;
 }

include/linux/hid.h

@@ -644,12 +644,13 @@ static inline void hid_set_drvdata(struct hid_device *hdev, void *data)
 struct hid_parser {
 	struct hid_global     global;
 	struct hid_global     global_stack[HID_GLOBAL_STACK_SIZE];
-	unsigned              global_stack_ptr;
+	unsigned int          global_stack_ptr;
 	struct hid_local      local;
-	unsigned              collection_stack[HID_COLLECTION_STACK_SIZE];
-	unsigned              collection_stack_ptr;
+	unsigned int         *collection_stack;
+	unsigned int          collection_stack_ptr;
+	unsigned int          collection_stack_size;
 	struct hid_device    *device;
-	unsigned              scan_flags;
+	unsigned int          scan_flags;
 };
 
 struct hid_class_descriptor {