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

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Message-ID: <c9baa43edbde4a6aab7ec32a25eec4dae7031443.camel@siemens.com>
Date: Tue, 1 Oct 2024 10:40:04 +0000
From: "Sverdlin, Alexander" <alexander.sverdlin@...mens.com>
To: "inguin@....de" <inguin@....de>, "linux-kernel@...r.kernel.org"
	<linux-kernel@...r.kernel.org>, "netdev@...r.kernel.org"
	<netdev@...r.kernel.org>
CC: "dmurphy@...com" <dmurphy@...com>
Subject: Re: [PATCH] net: phy: dp83869: fix memory corruption when enabling
 fiber

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@....de>
> ---
>  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