Re: [PATCH] media: dvb: check return value digitv_ctrl_msg

From: Dan Carpenter <dan.carpenter@oracle.com>
To: Sean Young <sean@mess.org>
Cc: Phong Tran <tranmanphong@gmail.com>,
	mchehab@kernel.org, gregkh@linuxfoundation.org,
	allison@lohutok.net, tglx@linutronix.de,
	syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com,
	linux-media@vger.kernel.org, linux-kernel@vger.kernel.org,
	glider@google.com, syzkaller-bugs@googlegroups.com
Subject: Re: [PATCH] media: dvb: check return value digitv_ctrl_msg
Date: Wed, 15 Jan 2020 21:15:18 +0300	[thread overview]
Message-ID: <20200115181315.GG9562@kadam> (raw)
In-Reply-To: <20200115180116.GA21151@kadam>

On Wed, Jan 15, 2020 at 09:01:17PM +0300, Dan Carpenter wrote:
> On Wed, Jan 15, 2020 at 05:32:26PM +0000, Sean Young wrote:
> > Hello,
> > 
> > On Tue, Dec 03, 2019 at 07:41:38AM +0700, Phong Tran wrote:
> > > For fixing syzbot "KMSAN: uninit-value in digitv_rc_query"
> > > 
> > > In scenario testing for syzbot, failure reading from
> > > digitv_ctrl_msg() [1].
> > > 
> > > Eg:
> > > [   91.846657][ T3844] dvb-usb: bulk message failed: -22 (7/0)
> > > 
> > > digitv_rc_query() always return 0. But in this case a wrong thing happens.
> > > 
> > > Reported-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> > > Tested-by: syzbot+6bf9606ee955b646c0e1@syzkaller.appspotmail.com
> > 
> > A fix for this was already merged I'm afraid, see commit eecc70d22ae5
> > ("media: digitv: don't continue if remote control state can't be read").
> > 
> > > [1]: https://syzkaller.appspot.com/text?tag=CrashLog&x=16860a63600000
> > > [2]: https://groups.google.com/d/msg/syzkaller-bugs/-TXIJAZ0J9Q/T4PEUQoeAQAJ
> > > 
> > > Signed-off-by: Phong Tran <tranmanphong@gmail.com>
> > > ---
> > >  drivers/media/usb/dvb-usb/digitv.c | 12 ++++++++----
> > >  1 file changed, 8 insertions(+), 4 deletions(-)
> > > 
> > > diff --git a/drivers/media/usb/dvb-usb/digitv.c b/drivers/media/usb/dvb-usb/digitv.c
> > > index dd5bb230cec1..61bc8945e6b9 100644
> > > --- a/drivers/media/usb/dvb-usb/digitv.c
> > > +++ b/drivers/media/usb/dvb-usb/digitv.c
> > > @@ -231,17 +231,21 @@ static struct rc_map_table rc_map_digitv_table[] = {
> > >  static int digitv_rc_query(struct dvb_usb_device *d, u32 *event, int *state)
> > >  {
> > >  	int i;
> > > -	u8 key[5];
> > > +	u8 key[5] = { 0 };
> > 
> > The merged commit does not change this line. Why was this changed?
> > 
> 
> It would fix the problem that key[0] is never initialized...  But the
> correct fix is to make key 4 elements long and delete key[0].

Phong,

Presumably you can fix this?  You will have to renumber key[1] to
key[0] and key[2] to key[1] etc...  Add a fixes tag.

Fixes: 774c0de4aed4 ("V4L/DVB (4616): [PATCH] Nebula DigiTV USB RC support")

Otherwise if you want I can send the patch.

regards,
dan carpenter