Re: [dpdk-stable] [dpdk-dev] [PATCH 1/9] net/pcap: fix argument checks

[Kevin Traynor <ktraynor@redhat.com>]

On 05/11/2019 17:10, Ferriter, Cian wrote:
> 
> 
>> -----Original Message-----
>> From: Kevin Traynor <ktraynor@redhat.com>
>> Sent: Tuesday 5 November 2019 16:41
>> To: David Marchand <david.marchand@redhat.com>
>> Cc: dev <dev@dpdk.org>; Ferriter, Cian <cian.ferriter@intel.com>; dpdk
>> stable <stable@dpdk.org>; Yigit, Ferruh <ferruh.yigit@intel.com>
>> Subject: Re: [dpdk-dev] [PATCH 1/9] net/pcap: fix argument checks
>>
>> On 30/10/2019 07:52, David Marchand wrote:
>>> On Tue, Oct 1, 2019 at 2:54 PM Kevin Traynor <ktraynor@redhat.com>
>> wrote:
>>>>
>>>> Previously rx/tx_queues were passed into eth_from_pcaps_common() as
>>>> ptrs and were checked for being NULL.
>>>>
>>>> In commit da6ba28f0540 ("net/pcap: use a struct to pass user
>>>> options") that changed to pass in a ptr to a pmd_devargs_all which
>>>> contains the rx/tx_queues.
>>>>
>>>> The parameter checking was not updated as part of that commit and
>>>> coverity caught that there was still a check if rx/tx_queues were
>>>> NULL, apparently after they had been dereferenced.
>>>>
>>>> Fix that by checking the pmd_devargs_all ptr and removing the NULL
>>>> checks on rx/tx_queues.
>>>>
>>>> 1231        struct pmd_devargs *rx_queues = &devargs_all->rx_queues;
>>>> 1232        struct pmd_devargs *tx_queues = &devargs_all->tx_queues;
>>>> 1233        const unsigned int nb_rx_queues = rx_queues->num_of_queue;
>>>>     deref_ptr: Directly dereferencing pointer tx_queues.
>>>> 1234        const unsigned int nb_tx_queues = tx_queues->num_of_queue;
>>>> 1235        unsigned int i;
>>>> 1236
>>>> 1237        /* do some parameter checking */
>>>>     CID 345004: Dereference before null check (REVERSE_INULL)
>>>>     [select issue]
>>>> 1238        if (rx_queues == NULL && nb_rx_queues > 0)
>>>> 1239                return -1;
>>>>     CID 345029 (#1 of 1): Dereference before null check (REVERSE_INULL)
>>>>     check_after_deref: Null-checking tx_queues suggests that it may be
>>>>     null, but it has already been dereferenced on all paths leading to
>>>>     the check.
>>>> 1240        if (tx_queues == NULL && nb_tx_queues > 0)
>>>> 1241                return -1;
>>>>
>>>> Coverity issue: 345029
>>>> Coverity issue: 345044
>>>> Fixes: da6ba28f0540 ("net/pcap: use a struct to pass user options")
>>>> Cc: cian.ferriter@intel.com
>>>> Cc: stable@dpdk.org
>>>>
>>>> Signed-off-by: Kevin Traynor <ktraynor@redhat.com>
>>>
>>> This patch hides the coverity warning.
>>> But can't we just remove those checks?
>>>
>>> Iiuc, the checks on NULL pointers are unnecessary since
>>>
>> https://git.dpdk.org/dpdk/commit/?id=a0fce1193ce13a50c00624cb36605ebe
>> f7a3e60b.
>>>
>>>
>>
>> Aside from the Coverity complaint about rxq/txq NULL check after use, the
>> checks didn't seem to make sense anymore as rxq/txq are part of devargs_all
>> struct now, so they were removed.
>>
>> I added the NULL check on devargs_all to avoid a NULL deference while
>> getting them instead. The check isn't doing any harm, but looking at the
>> current paths to this fn. can see devargs_all would not be NULL, so I'm ok to
>> remove it too. Cian/Ferruh, wdyt?
> 
> I'm OK to remove this. Looks like it's no longer necessary. Good find David!
> 

Thanks Cian, I kept your Ack for v2.