linux-kernel - Re: [PATCH] [media] dvb: avoid warning in dvb

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Message-ID: <20161027152502.GF42084@redhat.com>
Date:   Thu, 27 Oct 2016 11:25:02 -0400
From:   Jarod Wilson <jarod@...hat.com>
To:     Arnd Bergmann <arnd@...db.de>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        Hans Verkuil <hans.verkuil@...co.com>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [media] dvb: avoid warning in dvb_net

On Thu, Oct 27, 2016 at 05:09:28PM +0200, Arnd Bergmann wrote:
> On Thursday, October 27, 2016 10:13:27 AM CEST Jarod Wilson wrote:
> > On Thu, Oct 27, 2016 at 03:57:41PM +0200, Arnd Bergmann wrote:
> > > With gcc-5 or higher on x86, we can get a bogus warning in the
> > > dvb-net code:
> > > 
> > > drivers/media/dvb-core/dvb_net.c: In function ‘dvb_net_ule’:
> > > arch/x86/include/asm/string_32.h:77:14: error: ‘dest_addr’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
> > > drivers/media/dvb-core/dvb_net.c:633:8: note: ‘dest_addr’ was declared here
> > > 
> > > The problem here is that gcc doesn't track all of the conditions
> > > to prove it can't end up copying uninitialized data.
> > > This changes the logic around so we zero out the destination
> > > address earlier when we determine that it is not set here.
> > > This allows the compiler to figure it out.
> > > 
> > > Signed-off-by: Arnd Bergmann <arnd@...db.de>
> > > ---
> > >  drivers/media/dvb-core/dvb_net.c | 12 +++++-------
> > >  1 file changed, 5 insertions(+), 7 deletions(-)
> > > 
> > > diff --git a/drivers/media/dvb-core/dvb_net.c b/drivers/media/dvb-core/dvb_net.c
> > > index 088914c4623f..f1b416de9dab 100644
> > > --- a/drivers/media/dvb-core/dvb_net.c
> > > +++ b/drivers/media/dvb-core/dvb_net.c
> > > @@ -688,6 +688,9 @@ static void dvb_net_ule( struct net_device *dev, const u8 *buf, size_t buf_len )
> > >                                                             ETH_ALEN);
> > >                                               skb_pull(priv->ule_skb, ETH_ALEN);
> > >                                       }
> > > +                             } else {
> > > +                                      /* othersie use zero destination address */
> > 
> > I'm assuming you meant "otherwise" there instead of "othersie".
> > 
> 
> Yes, I sent a v2 now, thanks for taking a look. I assume this means
> you have no other objections to the patch?

No objections, but I don't know enough about ULE or it's handling there
to do an informed critique outside of the typo.

-- 
Jarod Wilson
jarod@...hat.com