media: mceusb: sanity check for prescaler value

prescaler larger than 8 would mean the carrier is at most 152Hz,
which does not make sense for IR carriers.

Reported-by: syzbot+6d31bf169a8265204b8d@syzkaller.appspotmail.com
Signed-off-by: Sean Young <sean@mess.org>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>

diff --git a/drivers/media/rc/mceusb.c b/drivers/media/rc/mceusb.c
index c8d63673e131df5fa182295927386b7cae0509cd..5642595a057ec422c1bca563674a2a94ec982049 100644 (file)
--- a/drivers/media/rc/mceusb.c
+++ b/drivers/media/rc/mceusb.c
@@ -701,11 +701,18 @@ static void mceusb_dev_printdata(struct mceusb_dev *ir, u8 *buf, int buf_len,
                                data[0], data[1]);
                        break;
                case MCE_RSP_EQIRCFS:
+                       if (!data[0] && !data[1]) {
+                               dev_dbg(dev, "%s: no carrier", inout);
+                               break;
+                       }
+                       // prescaler should make sense
+                       if (data[0] > 8)
+                               break;
                        period = DIV_ROUND_CLOSEST((1U << data[0] * 2) *
                                                   (data[1] + 1), 10);
                        if (!period)
                                break;
-                       carrier = (1000 * 1000) / period;
+                       carrier = USEC_PER_SEC / period;
                        dev_dbg(dev, "%s carrier of %u Hz (period %uus)",
                                 inout, carrier, period);
                        break;