Re: [PATCH] net: phy: dp83869: fix memory corruption when enabling fiber

[Sverdlin, Alexander]

Hi Ingo!

On Tue, 2024-10-01 at 09:57 +0200, Ingo van Lil wrote:
> When configuring the fiber port, the DP83869 PHY driver incorrectly
> calls linkmode_set_bit() with a bit mask (1 << 10) rather than a bit
> number (10). This corrupts some other memory location -- in case of
> arm64 the priv pointer in the same structure.
> 
> Signed-off-by: Ingo van Lil <inguin@xxxxxx>
> ---
>  drivers/net/phy/dp83869.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/net/phy/dp83869.c b/drivers/net/phy/dp83869.c
> index d7aaefb5226b..9c5ac5d6a9fd 100644
> --- a/drivers/net/phy/dp83869.c
> +++ b/drivers/net/phy/dp83869.c
> @@ -645,7 +645,7 @@ static int dp83869_configure_fiber(struct phy_device *phydev,
>  		     phydev->supported);
> 
>  	linkmode_set_bit(ETHTOOL_LINK_MODE_FIBRE_BIT, phydev->supported);
> -	linkmode_set_bit(ADVERTISED_FIBRE, phydev->advertising);
> +	linkmode_set_bit(ETHTOOL_LINK_MODE_FIBRE_BIT, phydev->advertising);

Are you sure this linkmode_set_bit() is required at all?

If we consider the following code at the very end of the same function?

        /* Update advertising from supported */
        linkmode_or(phydev->advertising, phydev->advertising,
                    phydev->supported);

> 
>  	if (dp83869->mode == DP83869_RGMII_1000_BASE) {
>  		linkmode_set_bit(ETHTOOL_LINK_MODE_1000baseX_Full_BIT,

-- 
Alexander Sverdlin
Siemens AG
www.siemens.com