netdev - Re: [PATCH net-next 1/3] ethtool: Ensure new ring parameters are within bounds during SRINGPARAM

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Date:   Mon, 8 Jan 2018 18:23:42 -0800
From:   Jakub Kicinski <kubakici@...pl>
To:     Tariq Toukan <tariqt@...lanox.com>
Cc:     "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
        Eran Ben Elisha <eranbe@...lanox.com>,
        Eugenia Emantayev <eugenia@...lanox.com>
Subject: Re: [PATCH net-next 1/3] ethtool: Ensure new ring parameters are
 within bounds during SRINGPARAM

On Mon,  8 Jan 2018 16:00:24 +0200, Tariq Toukan wrote:
> From: Eugenia Emantayev <eugenia@...lanox.com>
> 
> Add a sanity check to ensure that all requested ring parameters
> are within bounds, which should reduce errors in driver implementation.

(y)

> Signed-off-by: Eugenia Emantayev <eugenia@...lanox.com>
> Signed-off-by: Tariq Toukan <tariqt@...lanox.com>
> ---
>  net/core/ethtool.c | 13 +++++++++++--
>  1 file changed, 11 insertions(+), 2 deletions(-)
> 
> diff --git a/net/core/ethtool.c b/net/core/ethtool.c
> index 50a79203043b..9ea7cd52fde0 100644
> --- a/net/core/ethtool.c
> +++ b/net/core/ethtool.c
> @@ -1704,14 +1704,23 @@ static int ethtool_get_ringparam(struct net_device *dev, void __user *useraddr)
>  
>  static int ethtool_set_ringparam(struct net_device *dev, void __user *useraddr)
>  {
> -	struct ethtool_ringparam ringparam;
> +	struct ethtool_ringparam ringparam, max = { .cmd = ETHTOOL_GRINGPARAM };
>  
> -	if (!dev->ethtool_ops->set_ringparam)
> +	if (!dev->ethtool_ops->set_ringparam || !dev->ethtool_ops->get_ringparam)
>  		return -EOPNOTSUPP;
>  
>  	if (copy_from_user(&ringparam, useraddr, sizeof(ringparam)))
>  		return -EFAULT;
>  
> +	dev->ethtool_ops->get_ringparam(dev, &max);

Perhaps check the return value here?  It's pretty unlikely but
get_ringparam may fail.

> +	/* ensure new ring parameters are within the maximums */
> +	if (ringparam.rx_pending > max.rx_max_pending ||
> +	    ringparam.rx_mini_pending > max.rx_mini_max_pending ||
> +	    ringparam.rx_jumbo_pending > max.rx_jumbo_max_pending ||
> +	    ringparam.tx_pending > max.tx_max_pending)
> +		return -EINVAL;
> +
>  	return dev->ethtool_ops->set_ringparam(dev, &ringparam);
>  }
>