From f7b77ebe6d2f49c7747b2d619586d1aa33f9ea91 Mon Sep 17 00:00:00 2001
From: Michael Kuron <michael.kuron@gmail.com>
Date: Sun, 26 Sep 2021 21:51:26 +0100
Subject: [PATCH] media: dib0700: fix undefined behavior in tuner shutdown
Git-commit: f7b77ebe6d2f49c7747b2d619586d1aa33f9ea91
References: git-fixes
Patch-mainline: v5.17-rc1

This fixes a problem where closing the tuner would leave it in a state
where it would not tune to any channel when reopened. This problem was
discovered as part of https://github.com/hselasky/webcamd/issues/16.

Since adap->id is 0 or 1, this bit-shift overflows, which is undefined
behavior. The driver still worked in practice as the overflow would in
most environments result in 0, which rendered the line a no-op. When
running the driver as part of webcamd however, the overflow could lead
to 0xff due to optimizations by the compiler, which would, in the end,
improperly shut down the tuner.

The bug is a regression introduced in the commit referenced below. The
present patch causes identical behavior to before that commit for
adap->id equal to 0 or 1. The driver does not contain support for
dib0700 devices with more adapters, assuming such even exist.

Tests have been performed with the Xbox One Digital TV Tuner on amd64.
Not all dib0700 devices are expected to be affected by the regression;
this code path is only taken by those with incorrect endpoint numbers.

Link: https://lore.kernel.org/linux-media/1d2fc36d94ced6f67c7cc21dcc469d5e5bdd8201.1632689033.git.mchehab+huawei@kernel.org

Cc: stable@vger.kernel.org
Fixes: 7757ddda6f4f ("[media] DiB0700: add function to change I2C-speed")
Signed-off-by: Michael Kuron <michael.kuron@gmail.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>
Signed-off-by: Oliver Neukum <oneukum@suse.com>
---
 drivers/media/usb/dvb-usb/dib0700_core.c | 2 --
 1 file changed, 2 deletions(-)

diff --git a/drivers/media/usb/dvb-usb/dib0700_core.c b/drivers/media/usb/dvb-usb/dib0700_core.c
index 70219b3e8566..7ea8f68b0f45 100644
--- a/drivers/media/usb/dvb-usb/dib0700_core.c
+++ b/drivers/media/usb/dvb-usb/dib0700_core.c
@@ -618,8 +618,6 @@ int dib0700_streaming_ctrl(struct dvb_usb_adapter *adap, int onoff)
 		deb_info("the endpoint number (%i) is not correct, use the adapter id instead", adap->fe_adap[0].stream.props.endpoint);
 		if (onoff)
 			st->channel_state |=	1 << (adap->id);
-		else
-			st->channel_state |=	1 << ~(adap->id);
 	} else {
 		if (onoff)
 			st->channel_state |=	1 << (adap->fe_adap[0].stream.props.endpoint-2);
-- 
2.35.3