linux-kernel - Re: [PATCH v3] net: phy: micrel: fix crash when statistic requested for KSZ9031 phy

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Message-ID: <f14be9f1-1460-57a4-c255-94894ec50dcc@cogentembedded.com>
Date:   Thu, 13 Apr 2017 22:28:09 +0300
From:   Sergei Shtylyov <sergei.shtylyov@...entembedded.com>
To:     Grygorii Strashko <grygorii.strashko@...com>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Andrew Lunn <andrew@...n.ch>,
        Florian Fainelli <f.fainelli@...il.com>
Cc:     Sekhar Nori <nsekhar@...com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] net: phy: micrel: fix crash when statistic requested
 for KSZ9031 phy

On 04/13/2017 10:11 PM, Grygorii Strashko wrote:

> Now the command:
> 	ethtool --phy-statistics eth0
> will cause system crash with meassage "Unable to handle kernel NULL pointer
> dereference at virtual address 00000010" from:
>
>  (kszphy_get_stats) from [<c069f1d8>] (ethtool_get_phy_stats+0xd8/0x210)
>  (ethtool_get_phy_stats) from [<c06a0738>] (dev_ethtool+0x5b8/0x228c)
>  (dev_ethtool) from [<c06b5484>] (dev_ioctl+0x3fc/0x964)
>  (dev_ioctl) from [<c0679f7c>] (sock_ioctl+0x170/0x2c0)
>  (sock_ioctl) from [<c02419d4>] (do_vfs_ioctl+0xa8/0x95c)
>  (do_vfs_ioctl) from [<c02422c4>] (SyS_ioctl+0x3c/0x64)
>  (SyS_ioctl) from [<c0107d60>] (ret_fast_syscall+0x0/0x44)
>
> The reason: phy_driver structure for KSZ9031 phy has no .probe() callback
> defined. As result, struct phy_device *phydev->priv pointer will not be
> initializes (null).
> This issue will affect also following phys:
>  KSZ8795, KSZ886X, KSZ8873MLL, KSZ9031, KSZ9021, KSZ8061, KS8737
>
> Fix it by:
> - adding .probe() = kszphy_probe() callback to KSZ9031, KSZ9021
> phys. The kszphy_probe() can be re-used as it doesn't do any phy specific
> settings.
> - removing statistic callbacks from other phys (KSZ8795, KSZ886X,
> KSZ8873MLL, KSZ8061, KS8737) as they doesn't have corresponding
> statistic counters.

    Not sure how the 2nd change fixes the reported issue. It looks like a 
material for a separate patch...

> Fixes: 2b2427d06426 ("phy: micrel: Add ethtool statistics counters")
> Signed-off-by: Grygorii Strashko <grygorii.strashko@...com>
> Reviewed-by: Andrew Lunn <andrew@...n.ch>
[...]

MBR, Sergei