Subject: Re: [PATCH][next] net: dsa: sja1105: fix comparisons against uninitialized status fields

From: walter harms <[email-masked]>
Date: Tue, 07 May 2019 12:23:03 +0200

Am 07.05.2019 11:29, schrieb Colin Ian King:
> On 07/05/2019 10:20, Dan Carpenter wrote:
>> On Tue, May 07, 2019 at 09:44:58AM +0100, Colin King wrote:
>>> From: Colin Ian King <[email-masked]>
>>>
>>> The call to sja1105_status_get to set various fields in the status
>>> structure can potentially be skipped in a while-loop because of a couple
>>> of prior continuation jump paths. This can potientially lead to checking
>>> be checking against an uninitialized fields in the structure which may
>>> lead to unexpected results.  Fix this by ensuring all the fields in status
>>> are initialized to zero to be safe.
>>>
>>> Addresses-Coverity: ("Uninitialized scalar variable")
>>> Fixes: 8aa9ebccae87 ("net: dsa: Introduce driver for NXP SJA1105 5-port L2 switch")
>>> Signed-off-by: Colin Ian King <[email-masked]>
>>> ---
>>>  drivers/net/dsa/sja1105/sja1105_spi.c | 2 +-
>>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>>
>>> diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
>>> index 244a94ccfc18..76f6a51e10d9 100644
>>> --- a/drivers/net/dsa/sja1105/sja1105_spi.c
>>> +++ b/drivers/net/dsa/sja1105/sja1105_spi.c
>>> @@ -394,7 +394,7 @@ int sja1105_static_config_upload(struct sja1105_private *priv)
>>>  	struct sja1105_static_config *config = &priv->static_config;
>>>  	const struct sja1105_regs *regs = priv->info->regs;
>>>  	struct device *dev = &priv->spidev->dev;
>>> -	struct sja1105_status status;
>>> +	struct sja1105_status status = {};
>>
>> The exit condition isn't right.  It should continue if ret is negative
>> or the CRC stuff is invalid but right now it's ignoring ret.  It would
>> be better could just add a break statement at the very end and remove
>> the status checks.  Like so:
>>
>> diff --git a/drivers/net/dsa/sja1105/sja1105_spi.c b/drivers/net/dsa/sja1105/sja1105_spi.c
>> index 244a94ccfc18..3af3b0f3cc44 100644
>> --- a/drivers/net/dsa/sja1105/sja1105_spi.c
>> +++ b/drivers/net/dsa/sja1105/sja1105_spi.c
>> @@ -466,8 +466,9 @@ int sja1105_static_config_upload(struct sja1105_private *priv)
>>  				"invalid, retrying...\n");
>>  			continue;
>>  		}
>> -	} while (--retries && (status.crcchkl == 1 || status.crcchkg == 1 ||
>> -		 status.configs == 0 || status.ids == 1));
>> +		/* Success! */
>> +		break;
>> +	} while (--retries);
> 
> Good point, I'll send a V2 for that. Thanks Dan for your keen eyes.
> 

please do not put everything into the while condition.
It make that hard to read, just add if () break to detangle that.

re,
 wh

> Colin
>>  	if (!retries) {
>>  		rc = -EIO;