netdev - Re: [PATCH v1 net-next 2/2] igb: support SIOCSMIIREG

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Message-ID: <554BA646.1060000@gmail.com>
Date:	Thu, 07 May 2015 10:52:06 -0700
From:	Alexander Duyck <alexander.duyck@...il.com>
To:	Jonathan Toppins <jtoppins@...ulusnetworks.com>,
	jeffrey.t.kirsher@...el.com
CC:	jesse.brandeburg@...el.com, shannon.nelson@...el.com,
	carolyn.wyborny@...el.com, donald.c.skidmore@...el.com,
	matthew.vick@...el.com, john.ronciak@...el.com,
	mitch.a.williams@...el.com, intel-wired-lan@...ts.osuosl.org,
	netdev@...r.kernel.org, gospo@...ulusnetworks.com,
	shm@...ulusnetworks.com, Alan Liebthal <alanl@...ulusnetworks.com>
Subject: Re: [PATCH v1 net-next 2/2] igb: support SIOCSMIIREG

On 04/17/2015 01:24 PM, Jonathan Toppins wrote:
> From: Alan Liebthal <alanl@...ulusnetworks.com>
>
> Support setting the MII register via SIOCSMIIREG.
>
> Signed-off-by: Alan Liebthal <alanl@...ulusnetworks.com>
> Signed-off-by: Jonathan Toppins <jtoppins@...ulusnetworks.com>
> ---
>   drivers/net/ethernet/intel/igb/igb_main.c |    5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/net/ethernet/intel/igb/igb_main.c b/drivers/net/ethernet/intel/igb/igb_main.c
> index 720b785..1071a71 100644
> --- a/drivers/net/ethernet/intel/igb/igb_main.c
> +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> @@ -7141,6 +7141,11 @@ static int igb_mii_ioctl(struct net_device *netdev, struct ifreq *ifr, int cmd)
>   			return -EIO;
>   		break;
>   	case SIOCSMIIREG:
> +		adapter->hw.phy.addr = data->phy_id;
> +		if (igb_write_phy_reg(&adapter->hw, data->reg_num & 0x1F,
> +				      data->val_in))
> +			return -EIO;
> +		break;
>   	default:
>   		return -EOPNOTSUPP;
>   	}

How and why is this being used?  From what I can tell it looks like it 
is an easy way to break any of the existing interfaces if it is misused 
since all you would need to do is specify a phy address that doesn't 
match the existing PHY in the system and then you would likely lose 
link, or possibly mess up the configuration on the system requiring.

I suspect this is a back door for some piece of user space code that is 
being given far more permission than it should be.

- Alex
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