From 9dec0f48a75e0dadca498002d25ef4e143e60194 Mon Sep 17 00:00:00 2001
From: Sean Young <sean@mess.org>
Date: Tue, 19 Jan 2021 14:53:50 +0100
Subject: [PATCH] media: mceusb: sanity check for prescaler value
Git-commit: 9dec0f48a75e0dadca498002d25ef4e143e60194
References: git-fixes
Patch-mainline: v5.12-rc1

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>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/media/rc/mceusb.c |    9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

--- a/drivers/media/rc/mceusb.c
+++ b/drivers/media/rc/mceusb.c
@@ -630,11 +630,18 @@ static void mceusb_dev_printdata(struct
 				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;