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[204.195.22.127]) by smtp.gmail.com with ESMTPSA id k8sm17733768pgq.37.2019.03.14.08.44.40 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 14 Mar 2019 08:44:40 -0700 (PDT) Date: Thu, 14 Mar 2019 08:44:35 -0700 From: Stephen Hemminger To: Matan Azrad Cc: "dev@dpdk.org" Message-ID: <20190314084435.2cca9735@shemminger-XPS-13-9360> In-Reply-To: References: <20190313021253.525-1-stephen@networkplumber.org> MIME-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Subject: Re: [dpdk-dev] [PATCH] net/vdev_netvsc: fix erronous cast X-BeenThere: dev@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: DPDK patches and discussions List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: dev-bounces@dpdk.org Sender: "dev" Message-ID: <20190314154435.zKElsFbptmzBI6EdO1TSWVZI8Ux8dzke9Y6g-M6o6AM@z> On Thu, 14 Mar 2019 11:13:10 +0000 Matan Azrad wrote: > Hi > > From: Stephen Hemminger > > The return value from bus->find_device is a rte_device which is not safe to > > cast to a rte_vdev_device structure. > > It doesn't really matter since only being checked for NULL but static checkers > > might find a bug here. > > > > Fix line is missing. > > > Signed-off-by: Stephen Hemminger > > --- > > drivers/net/vdev_netvsc/vdev_netvsc.c | 7 ++++--- > > 1 file changed, 4 insertions(+), 3 deletions(-) > > > > diff --git a/drivers/net/vdev_netvsc/vdev_netvsc.c > > b/drivers/net/vdev_netvsc/vdev_netvsc.c > > index ba63fac2a598..801f54c96e01 100644 > > --- a/drivers/net/vdev_netvsc/vdev_netvsc.c > > +++ b/drivers/net/vdev_netvsc/vdev_netvsc.c > > @@ -808,7 +808,7 @@ vdev_netvsc_cmp_rte_device(const struct > > rte_device *dev1, static void vdev_netvsc_scan_callback(__rte_unused > > void *arg) { > > - struct rte_vdev_device *dev; > > + struct rte_device *dev; > > struct rte_devargs *devargs; > > struct rte_bus *vbus = rte_bus_find_by_name("vdev"); > > > > @@ -816,8 +816,9 @@ vdev_netvsc_scan_callback(__rte_unused void *arg) > > if (!strncmp(devargs->name, VDEV_NETVSC_DRIVER_NAME, > > VDEV_NETVSC_DRIVER_NAME_LEN)) > > return; > > - dev = (struct rte_vdev_device *)vbus->find_device(NULL, > > - vdev_netvsc_cmp_rte_device, > > VDEV_NETVSC_DRIVER_NAME); > > + > > + dev = vbus->find_device(NULL, vdev_netvsc_cmp_rte_device, > > + VDEV_NETVSC_DRIVER_NAME); > > Since the device must be vdev here, > It is better to use explicit cast to make the checker happy. The cast is converting from rte_device to rte_vdev_device which incorrect. The device returned by vbus->find_device is a rte_device not a rte_vdev_device: vbus->find_device points to rte_vdev_find_device struct rte_device * rte_vdev_find_device(const struct rte_device *start, rte_dev_cmp_t cmp, const void *data) but definition of rte_vdev_device is: struct rte_vdev_device { TAILQ_ENTRY(rte_vdev_device) next; /**< Next attached vdev */ struct rte_device device; /**< Inherit core device */ }; The only safe way to get rte_vdev_device would be to use container_of(). dev = vbus->find_device(NULL, vdev_netvsc_cmp_rte_device, VDEV_NETVSC_DRIVER_NAME); vdev = dev ? container_of(dev, struct rte_vdev_device, device) : NULL; But as the PATCH demonstrated, this is not necessary.