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

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Message-ID: <87618083B2453E4A8714035B62D67992337C63A8@FMSMSX102.amr.corp.intel.com>
Date:	Wed, 20 Feb 2013 00:26:37 +0000
From:	"Tantilov, Emil S" <emil.s.tantilov@...el.com>
To:	Ben Hutchings <bhutchings@...arflare.com>,
	"Kirsher, Jeffrey T" <jeffrey.t.kirsher@...el.com>,
	Aurélien Guillaume <footplus@...il.com>
CC:	"davem@...emloft.net" <davem@...emloft.net>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"gospo@...hat.com" <gospo@...hat.com>,
	"sassmann@...hat.com" <sassmann@...hat.com>
Subject: RE: [net-next 13/15] ixgbe: implement SFF diagnostic monitoring via
 ethtool

>-----Original Message-----
>From: Ben Hutchings [mailto:bhutchings@...arflare.com]
>Sent: Tuesday, February 19, 2013 2:14 PM
>To: Kirsher, Jeffrey T; Aurélien Guillaume
>Cc: davem@...emloft.net; netdev@...r.kernel.org; gospo@...hat.com;
>sassmann@...hat.com; Tantilov, Emil S
>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.

Thanks Ben, we'll address this in a follow up patch.

Emil