[net] net: phy: guard against accessing a NULL features bitmap

Since phy driver features became a link_mode bitmap, phy drivers that
don't have a list of features configured will cause the kernel to crash
when probed.

Fixes: 719655a14971 ("net: phy: Replace phy driver features u32 with link_mode bitmap")
Reported-by: Scott Wood <oss@buserror.net>
Signed-off-by: Camelia Groza <camelia.groza@nxp.com>
---
I'll submit a modified version of this patch to 4.20 stable once this
one is accepted.
---
 drivers/net/phy/phy_device.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

On Fri, Jan 11, 2019 at 01:56:46PM +0200, Camelia Groza wrote:
> Since phy driver features became a link_mode bitmap, phy drivers that
> don't have a list of features configured will cause the kernel to crash
> when probed.

Hi Camelia

A NULL features is a driver bug. So i would prefer to solve this
differently.

Please make phy_driver_register() do a WARN_ON(!new_driver->features)
and return -EINVAL.

Do you know of a specific driver which as a NULL value? We should fix
that as well.

Thank
	Andrew

> -----Original Message-----
> From: Andrew Lunn <andrew@lunn.ch>
> Sent: Friday, January 11, 2019 15:38
> To: Camelia Alexandra Groza <camelia.groza@nxp.com>
> Cc: f.fainelli@gmail.com; hkallweit1@gmail.com; davem@davemloft.net;
> oss@buserror.net; netdev@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: Re: [PATCH net] net: phy: guard against accessing a NULL features
> bitmap
> 
> On Fri, Jan 11, 2019 at 01:56:46PM +0200, Camelia Groza wrote:
> > Since phy driver features became a link_mode bitmap, phy drivers that
> > don't have a list of features configured will cause the kernel to crash
> > when probed.
> 
> Hi Camelia
> 
> A NULL features is a driver bug. So i would prefer to solve this
> differently.
>
> Please make phy_driver_register() do a WARN_ON(!new_driver->features)
> and return -EINVAL.

I wasn't aware that features are mandatory. I'll make the change.

> Do you know of a specific driver which as a NULL value? We should fix
> that as well.

Yes, there are five drivers that don't have features configured: BCM8706, BCM8727, CS4340, TN2020 and KSZ8873MLL.

I'm planning to send patches on net-next for the Cortina and Teranetics ones at least, but fixing the generic crash was my priority.

Thanks,
Camelia

> > Hi Camelia
> > 
> > A NULL features is a driver bug. So i would prefer to solve this
> > differently.
> >
> > Please make phy_driver_register() do a WARN_ON(!new_driver->features)
> > and return -EINVAL.
> 
> I wasn't aware that features are mandatory. I'll make the change.

It was not origionally, but really it should be now.

> Yes, there are five drivers that don't have features configured: BCM8706, BCM8727, CS4340, TN2020 and KSZ8873MLL.

> I'm planning to send patches on net-next for the Cortina and
> Teranetics ones at least, but fixing the generic crash was my
> priority.

O.K, will take the others.

Thanks
	Andrew