Subject: Re: [PATCH] staging: octeon-ethernet: trivial: Avoid OOPS if phydev is not set

From: Dan Carpenter <[email-masked]>
Date: Mon, 14 Oct 2013 22:16:49 +0300

On Mon, Oct 14, 2013 at 09:39:06PM +0300, Aaro Koskinen wrote:
> Hi,
> 
> On Mon, Oct 14, 2013 at 01:10:51PM +0300, Dan Carpenter wrote:
> > On Sun, Oct 13, 2013 at 02:28:10PM -0700, Greg KH wrote:
> > > On Sun, Oct 13, 2013 at 08:59:54PM +0200, Sebastian Pöhn wrote:
> > > > A zero pointer deref on priv->phydev->link was causing oops on our systems.
> > > > Might be related to improper configuration but we should fail gracefully here ;-)
> > > > 
> > > > Signed-off-by: Sebastian Poehn <[email-masked]>
> > > > 
> > > > ---
> > > > 
> > > > diff --git a/drivers/staging/octeon/ethernet-mdio.c b/drivers/staging/octeon/ethernet-mdio.c
> > > > index 83b1030..bc8c503 100644
> > > > --- a/drivers/staging/octeon/ethernet-mdio.c
> > > > +++ b/drivers/staging/octeon/ethernet-mdio.c
> > > > @@ -121,6 +121,9 @@ static void cvm_oct_adjust_link(struct net_device *dev)
> > > >         struct octeon_ethernet *priv = netdev_priv(dev);
> > > >         cvmx_helper_link_info_t link_info;
> > > >  
> > > > +       if(!priv->phydev)
> > > > +               return ;
> > > 
> > > Please always run your patches through the scripts/checkpatch.pl tool so
> > > that maintainers don't have to point out the obvious coding syle errors
> > > by hand each time :)
> > 
> > Also it's whitespace damaged and doesn't apply.
> > 
> > > 
> > > Care to try again?
> > > 
> > > Also, how was phydev NULL?  What was causing that?
> > 
> > To me it looks like phydev is always NULL.
> 
> It's initialized in cvm_oct_phy_setup_device():
> 
> 	priv->phydev = of_phy_connect(dev, phy_node, cvm_oct_adjust_link, 0,
        ^^^^^^^^^^^^                                 ^^^^^^^^^^^^^^^^^^^

Sorry I should have explained better.

We use cvm_oct_adjust_link() to initialize priv->phydev but
cvm_oct_adjust_link() depends on priv->phydev.  It seems like we would
hit the NULL dereference every time.  Weird huh?

regards,
dan carpenter