netdev - Re: [net-next 13/15] ixgbe: implement SFF diagnostic monitoring via ethtool

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Message-ID: <1361312048.2967.44.camel@bwh-desktop.uk.solarflarecom.com>
Date:	Tue, 19 Feb 2013 22:14:08 +0000
From:	Ben Hutchings <bhutchings@...arflare.com>
To:	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Aurélien Guillaume <footplus@...il.com>
CC:	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	<gospo@...hat.com>, <sassmann@...hat.com>,
	Emil Tantilov <emil.s.tantilov@...el.com>
Subject: Re: [net-next 13/15] ixgbe: implement SFF diagnostic monitoring via
 ethtool

On Sat, 2013-02-16 at 00:33 -0800, Jeff Kirsher wrote:
> From: Aurélien Guillaume <footplus@...il.com>
> 
> This patch adds support for reading data from SFP+ modules over i2c.
[...]
> --- a/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
> +++ b/drivers/net/ethernet/intel/ixgbe/ixgbe_ethtool.c
[...]
> +static int ixgbe_get_module_eeprom(struct net_device *dev,
> +					 struct ethtool_eeprom *ee,
> +					 u8 *data)
> +{
> +	struct ixgbe_adapter *adapter = netdev_priv(dev);
> +	struct ixgbe_hw *hw = &adapter->hw;
> +	u32 status = IXGBE_ERR_PHY_ADDR_INVALID;
> +	u8 databyte = 0xFF;
> +	int i = 0;
> +	int ret_val = 0;
> +
> +	/* ixgbe_get_module_info is called before this function in all
> +	 * cases, so we do not need any checks we already do above,
> +	 * and can trust ee->len to be a known value.
> +	 */
[...]

Whatever makes you think that?

All you are guaranteed is that:
    ee->offset <= ee->offset + ee->len <= eeprom_len
Same as for the regular EEPROM read function.

This implementation doesn't result in a heap overrun at present because
the caller allocates a whole page as a buffer.  But you should not
assume that it's safe to write more than ee->len bytes, nor that
ee->offset == 0.

Ben.

-- 
Ben Hutchings, Staff Engineer, Solarflare
Not speaking for my employer; that's the marketing department's job.
They asked us to note that Solarflare product names are trademarked.

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