linux-kernel - Re: [PATCH] media: dvb: check return value digitv_ctrl

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Date:   Wed, 15 Jan 2020 21:01:17 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Sean Young <sean@...s.org>
Cc:     Phong Tran <tranmanphong@...il.com>, mchehab@...nel.org,
        gregkh@...uxfoundation.org, allison@...utok.net,
        tglx@...utronix.de,
        syzbot+6bf9606ee955b646c0e1@...kaller.appspotmail.com,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        glider@...gle.com, syzkaller-bugs@...glegroups.com
Subject: Re: [PATCH] media: dvb: check return value digitv_ctrl_msg

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@...kaller.appspotmail.com
> > Tested-by: syzbot+6bf9606ee955b646c0e1@...kaller.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@...il.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].

regards,
dan carpenter