HID: validate HID report id size

The "Report ID" field of a HID report is used to build indexes of
reports. The kernel's index of these is limited to 256 entries, so any
malicious device that sets a Report ID greater than 255 will trigger
memory corruption on the host:

[ 1347.156239] BUG: unable to handle kernel paging request at ffff88094958a878
[ 1347.156261] IP: [<ffffffff813e4da0>] hid_register_report+0x2a/0x8b

CVE-2013-2888
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: stable@kernel.org
Signed-off-by: Jiri Kosina <jkosina@suse.cz>

drivers/hid/hid-core.c

@@ -63,6 +63,8 @@ struct hid_report *hid_register_report(struct hid_device *device, unsigned type,
 	struct hid_report_enum *report_enum = device->report_enum + type;
 	struct hid_report *report;
 
+	if (id >= HID_MAX_IDS)
+		return NULL;
 	if (report_enum->report_id_hash[id])
 		return report_enum->report_id_hash[id];
 
@@ -404,8 +406,10 @@ static int hid_parser_global(struct hid_parser *parser, struct hid_item *item)
 
 	case HID_GLOBAL_ITEM_TAG_REPORT_ID:
 		parser->global.report_id = item_udata(item);
-		if (parser->global.report_id == 0) {
-			hid_err(parser->device, "report_id 0 is invalid\n");
+		if (parser->global.report_id == 0 ||
+		    parser->global.report_id >= HID_MAX_IDS) {
+			hid_err(parser->device, "report_id %u is invalid\n",
+				parser->global.report_id);
 			return -1;
 		}
 		return 0;
@@ -575,7 +579,7 @@ static void hid_close_report(struct hid_device *device)
 	for (i = 0; i < HID_REPORT_TYPES; i++) {
 		struct hid_report_enum *report_enum = device->report_enum + i;
 
-		for (j = 0; j < 256; j++) {
+		for (j = 0; j < HID_MAX_IDS; j++) {
 			struct hid_report *report = report_enum->report_id_hash[j];
 			if (report)
 				hid_free_report(report);

include/linux/hid.h

@@ -393,10 +393,12 @@ struct hid_report {
 	struct hid_device *device;			/* associated device */
 };
 
+#define HID_MAX_IDS 256
+
 struct hid_report_enum {
 	unsigned numbered;
 	struct list_head report_list;
-	struct hid_report *report_id_hash[256];
+	struct hid_report *report_id_hash[HID_MAX_IDS];
 };
 
 #define HID_REPORT_TYPES 3