USB: serial: garmin_gps: add sanity checking for data length

BugLink: https://bugs.launchpad.net/bugs/1881356

commit e9b3c610 upstream.

We must not process packets shorter than a packet ID
Signed-off-by: Oliver Neukum <oneukum@suse.com>
Reported-and-tested-by: syzbot+d29e9263e13ce0b9f4fd@syzkaller.appspotmail.com
Fixes: 1da177e4 ("Linux-2.6.12-rc2")
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Johan Hovold <johan@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Ian May <ian.may@canonical.com>
Signed-off-by: Kelsey Skunberg <kelsey.skunberg@canonical.com>

drivers/usb/serial/garmin_gps.c

@@ -1162,8 +1162,8 @@ static void garmin_read_process(struct garmin_data *garmin_data_p,
 		   send it directly to the tty port */
 		if (garmin_data_p->flags & FLAGS_QUEUING) {
 			pkt_add(garmin_data_p, data, data_length);
-		} else if (bulk_data ||
-			   getLayerId(data) == GARMIN_LAYERID_APPL) {
+		} else if (bulk_data || (data_length >= sizeof(u32) &&
+				getLayerId(data) == GARMIN_LAYERID_APPL)) {
 
 			spin_lock_irqsave(&garmin_data_p->lock, flags);
 			garmin_data_p->flags |= APP_RESP_SEEN;