netdev - Re: [PATCH RFC 7/7] net: phy: read MMD ID from all present MMDs

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Date:   Tue, 26 May 2020 10:35:46 -0500
From:   Jeremy Linton <jeremy.linton@....com>
To:     Russell King <rmk+kernel@...linux.org.uk>,
        Andrew Lunn <andrew@...n.ch>,
        Heiner Kallweit <hkallweit1@...il.com>
Cc:     Florian Fainelli <f.fainelli@...il.com>, netdev@...r.kernel.org
Subject: Re: [PATCH RFC 7/7] net: phy: read MMD ID from all present MMDs

Hi,

On 5/26/20 9:31 AM, Russell King wrote:
> Expand the device_ids[] array to allow all MMD IDs to be read rather
> than just the first 8 MMDs, but only read the ID if the MDIO_STAT2
> register reports that a device really is present here for these new
> devices to maintain compatibility with our current behaviour.
> 
> 88X3310 PHY vendor MMDs do are marked as present in the
> devices_in_package, but do not contain IEE 802.3 compatible register
> sets in their lower space.  This avoids reading incorrect values as MMD
> identifiers.
> 
> Signed-off-by: Russell King <rmk+kernel@...linux.org.uk>
> ---
>   drivers/net/phy/phy_device.c | 14 ++++++++++++++
>   include/linux/phy.h          |  2 +-
>   2 files changed, 15 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/phy_device.c b/drivers/net/phy/phy_device.c
> index 1c948bbf4fa0..92742c7be80f 100644
> --- a/drivers/net/phy/phy_device.c
> +++ b/drivers/net/phy/phy_device.c
> @@ -773,6 +773,20 @@ static int get_phy_c45_ids(struct mii_bus *bus, int addr, u32 *phy_id,
>   		if (!(devs_in_pkg & (1 << i)))
>   			continue;
>   
> +		if (i >= 8) {
> +			/* Only probe the MMD ID for MMDs >= 8 if they report
> +			 * that they are present. We have at least one PHY that
> +			 * reports MMD presence in devs_in_pkg, but does not
> +			 * contain valid IEEE 802.3 ID registers in some MMDs.
> +			 */
> +			ret = phy_c45_probe_present(bus, addr, i);
> +			if (ret < 0)
> +				return ret;
> +
> +			if (!ret)
> +				continue;
> +		}
> +
>   		phy_reg = mdiobus_c45_read(bus, addr, i, MII_PHYSID1);
>   		if (phy_reg < 0)
>   			return -EIO;
> diff --git a/include/linux/phy.h b/include/linux/phy.h
> index 0d41c710339a..3325dd8fb9ac 100644
> --- a/include/linux/phy.h
> +++ b/include/linux/phy.h
> @@ -361,7 +361,7 @@ enum phy_state {
>   struct phy_c45_device_ids {
>   	u32 devices_in_package;
>   	u32 mmds_present;
> -	u32 device_ids[8];
> +	u32 device_ids[MDIO_MMD_NUM];

You have a array overflow/invalid access if you don't do this earlier in 
4/7.


>   };
>   
>   struct macsec_context;
>