Re:

["Gaëtan Rivet" <grive@u256.net>]

On Thu, Feb 10, 2022, at 16:00, Ferruh Yigit wrote:
> On 2/10/2022 7:10 AM, madhuker.mythri@oracle.com wrote:
>> From: Madhuker Mythri <madhuker.mythri@oracle.com>
>> 
>> Failsafe pmd started crashing with global devargs syntax as devargs is
>> not memset to zero. Access it to in rte_devargs_parse resulted in a
>> crash when called from secondary process.
>> 
>> Bugzilla Id: 933
>> 
>> Signed-off-by: Madhuker Mythri <madhuker.mythri@oracle.com>
>> ---
>>   drivers/net/failsafe/failsafe.c | 1 +
>>   1 file changed, 1 insertion(+)
>> 
>> diff --git a/drivers/net/failsafe/failsafe.c b/drivers/net/failsafe/failsafe.c
>> index 3c754a5f66..aa93cc6000 100644
>> --- a/drivers/net/failsafe/failsafe.c
>> +++ b/drivers/net/failsafe/failsafe.c
>> @@ -360,6 +360,7 @@ rte_pmd_failsafe_probe(struct rte_vdev_device *vdev)
>>   			if (sdev->devargs.name[0] == '\0')
>>   				continue;
>>   
>> +			memset(&devargs, 0, sizeof(devargs));
>>   			/* rebuild devargs to be able to get the bus name. */
>>   			ret = rte_devargs_parse(&devargs,
>>   						sdev->devargs.name);
>
> if 'rte_devargs_parse()' requires 'devargs' parameter to be memset,
> what do you think memset it in the API?
> This prevents forgotten cases like this.

Hi,

I was looking at it this morning.
Before the last release, rte_devargs_parse() was only supporting legacy syntax.
It never read from the devargs structure, only wrote to it. So it was safe to
use with a non-memset devargs.

The rte_devargs_layer_parse() however is more complex. To allow rte_dev_iterator_init() to call it without doing memory allocation, it reads parts of the devargs to make decisions.

Doing a first call to rte_devargs_layer_parse() as part of rte_devargs_parse() thus
modified the contract it had with the users, that it would never read from devargs.

It is not possible to completely avoid reading from devargs in rte_devargs_layer_parse().
It is necessary for RTE_DEV_FOREACH() to be safe to interrupt without having to do iterator cleanup.

This is my current understanding. In that context, yes I think it is preferrable to
do memset() within rte_devargs_parse(). It will restore the previous part of the API saying that calling it with non-memset devargs was safe to do.

Thanks,
-- 
Gaetan Rivet