--- zzzz-none-000/linux-4.4.60/drivers/input/tablet/gtco.c	2017-04-08 07:53:53.000000000 +0000
+++ scorpion-7490-727/linux-4.4.60/drivers/input/tablet/gtco.c	2021-02-04 17:41:59.000000000 +0000
@@ -231,13 +231,17 @@
 
 	/* Walk  this report and pull out the info we need */
 	while (i < length) {
-		prefix = report[i];
-
-		/* Skip over prefix */
-		i++;
+		prefix = report[i++];
 
 		/* Determine data size and save the data in the proper variable */
-		size = PREF_SIZE(prefix);
+		size = (1U << PREF_SIZE(prefix)) >> 1;
+		if (i + size > length) {
+			dev_err(ddev,
+				"Not enough data (need %d, have %d)\n",
+				i + size, length);
+			break;
+		}
+
 		switch (size) {
 		case 1:
 			data = report[i];
@@ -245,8 +249,7 @@
 		case 2:
 			data16 = get_unaligned_le16(&report[i]);
 			break;
-		case 3:
-			size = 4;
+		case 4:
 			data32 = get_unaligned_le32(&report[i]);
 			break;
 		}