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

["Ferriter, Cian" <cian.ferriter@intel.com>]

> -----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!