hid: asus: asus_report_fixup: fix potential read out of bounds

syzbot reported a potential read out of bounds in asus_report_fixup.

this patch adds checks so that a read out of bounds will not occur

Signed-off-by: Andrew Ballance <[email protected]>
Reported-by:  <[email protected]>
Closes: https://syzkaller.appspot.com/bug?extid=07762f019fd03d01f04c
Fixes: 59d2f5b ("HID: asus: fix more n-key report descriptors if n-key quirked")
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Benjamin Tissoires <[email protected]>

Author: mrwigglewaffles

drivers/hid/hid-asus.c

@@ -1204,8 +1204,8 @@ static __u8 *asus_report_fixup(struct hid_device *hdev, __u8 *rdesc,
 	}
 
 	/* match many more n-key devices */
-	if (drvdata->quirks & QUIRK_ROG_NKEY_KEYBOARD) {
-		for (int i = 0; i < *rsize + 1; i++) {
+	if (drvdata->quirks & QUIRK_ROG_NKEY_KEYBOARD && *rsize > 15) {
+		for (int i = 0; i < *rsize - 15; i++) {
 			/* offset to the count from 0x5a report part always 14 */
 			if (rdesc[i] == 0x85 && rdesc[i + 1] == 0x5a &&
 			    rdesc[i + 14] == 0x95 && rdesc[i + 15] == 0x05) {