Re: [dpdk-dev] [PATCH v2] ethdev: avoid usage of uninit device info in bad port case

[Andrew Rybchenko <arybchenko@solarflare.com>]

On 7/23/19 4:14 PM, Thomas Monjalon wrote:
> 23/07/2019 14:11, Andrew Rybchenko:
>> rte_eth_dev_info_get() returns void and caller does know if the function
>> does its job or not. Changing of the return value to int would be
>> API/ABI breakage which requires deprecation process and cannot be
>> backported to stable branches. For now, make sure that device info is
>> initialized even in the case of invalid port ID.
>>
>> Fixes: a30268e9a2d0 ("ethdev: reset whole dev info structure before filling")
>> Cc: stable@dpdk.org
>>
>> Signed-off-by: Andrew Rybchenko <arybchenko@solarflare.com>
>> ---
>> --- a/lib/librte_ethdev/rte_ethdev.c
>> +++ b/lib/librte_ethdev/rte_ethdev.c
>> +	/*
>> +	 * Init dev_info before port_id check since caller does not have
>> +	 * return status and does not know if get is successful or not.
>> +	 */
>> +	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
> If someone was using a canary to detect failure, it will be resetted.

I've not thought about such ways to check. I would expected check
for not NULL device or driver_name. It is not defined behaviour of
the function to not touch dev_info in the case of bad port ID.

> Why is it urgent to have this workaround?

Nothing really urgent, but I still think that it is a right fix to be
applied and backported to stable branches.
I really met calls with invalid port ID and it took some time
to understand where uninitialized data come from.

> Can we wait one more release for the definitive fix with error code?

No strong opinion, but definitive fix will not be backported.

>> +
>>   	RTE_ETH_VALID_PORTID_OR_RET(port_id);
>>   	dev = &rte_eth_devices[port_id];
>>   
>> -	memset(dev_info, 0, sizeof(struct rte_eth_dev_info));
>>   	dev_info->rx_desc_lim = lim;
>>   	dev_info->tx_desc_lim = lim;
>>   	dev_info->device = dev->device;
>>