Re: [Qemu-devel] [PATCH V4 for 3.1 4/4] virtio-net-test: add large tx buffer test

[Jason Wang]

On 2018/12/4 上午12:46, Eric Blake wrote:
> On 12/3/18 4:06 AM, Jason Wang wrote:
> > This test tries to build a packet whose size is greater than INT_MAX
> > which tries to trigger integer overflow in qemu_net_queue_append_iov()
> > which may result OOB.
>
> Can you also add a packet just slightly larger than NET_BUFSIZE (68k) 
> to show that we aren't having any further issues at even smaller (and 
> more likely) values of oversized packets?


Ok.


> > Signed-off-by: Jason Wang <address@hidden>
> > ---
> >   tests/virtio-net-test.c | 44 +++++++++++++++++++++++++++++++++++++++++
> >   1 file changed, 44 insertions(+)
>
> > +++ b/tests/virtio-net-test.c
> > @@ -245,6 +245,49 @@ static void pci_basic(gconstpointer data)
> >       g_free(dev);
> >       qtest_shutdown(qs);
> >   }
> > +
> > +static void large_tx(gconstpointer data)
> > +{
> > +    QVirtioPCIDevice *dev;
> > +    QOSState *qs;
> > +    QVirtQueuePCI *tx, *rx;
> > +    QVirtQueue *vq;
> > +    uint64_t req_addr;
> > +    uint32_t free_head;
> > +    size_t alloc_size = UINT_MAX / 64;
> > +    int i;
> > +
> > +    qs = pci_test_start("-netdev hubport,id=hp0,hubid=0 "
> > +                        "-device virtio-net-pci,netdev=hp0 ");
>
> Why the trailing space?


I guess this is a cut and paste error.


> > +    dev = virtio_net_pci_init(qs->pcibus, PCI_SLOT);
> > +
> > +    rx = (QVirtQueuePCI *)qvirtqueue_setup(&dev->vdev, qs->alloc, 0);
> > +    tx = (QVirtQueuePCI *)qvirtqueue_setup(&dev->vdev, qs->alloc, 1);
> > +
> > +    driver_init(&dev->vdev);
> > +    vq = &tx->vq;
> > +
> > +    /* Bypass the limitation by pointing several descriptors to a 
> > single
> > +     * smaller area */
> > +    req_addr = guest_alloc(qs->alloc, alloc_size);
> > +    free_head = qvirtqueue_add(vq, req_addr, alloc_size, false, true);
> > +
> > +    for (i = 0; i < 64; i++) {
> > +        qvirtqueue_add(vq, req_addr, alloc_size, false, i == 63 ?
> > +                       false : true);
>
> Any time I see both 'true' and 'false' in a ?: operator, I have to 
> wonder why you didn't just write the simpler version directly on the 
> condition.  This is the same as  'i != 63'.

Ok.


> > +    }
> > +    qvirtqueue_kick(&dev->vdev, vq, free_head);
> > +
> > +    qvirtio_wait_used_elem(&dev->vdev, vq, free_head, NULL,
> > +                           QVIRTIO_NET_TIMEOUT_US);
> > +
> > +    qvirtqueue_cleanup(dev->vdev.bus, &tx->vq, qs->alloc);
> > +    qvirtqueue_cleanup(dev->vdev.bus, &rx->vq, qs->alloc);
> > +    qvirtio_pci_device_disable(dev);
> > +    g_free(dev->pdev);
> > +    g_free(dev);
> > +    qtest_shutdown(qs);
> > +}
> >   #endif
> >     static void hotplug(void)
> > @@ -270,6 +313,7 @@ int main(int argc, char **argv)
> >       qtest_add_data_func("/virtio/net/pci/basic", send_recv_test, 
> > pci_basic);
> >       qtest_add_data_func("/virtio/net/pci/rx_stop_cont",
> >                           stop_cont_test, pci_basic);
> > +    qtest_add_data_func("/virtio/net/pci/large_tx", NULL, large_tx);
> >   #endif
> >       qtest_add_func("/virtio/net/pci/hotplug", hotplug);
>
> I can reproduce Peter's complaints of this introducing noise to 'make 
> check':
> qemu-system-x86_64: warning: hub 0 is not connected to host network


Yes, this is intended since the test does not require any host network. 
I will add a patch to suppress this warning if qtest is enabled.


> With patches 2-4 applied but patch 1 omitted, 'make check' fails with:
>
> Broken pipe
> tests/libqtest.c:125: kill_qemu() detected QEMU death from signal 11 
> (Segmentation fault) (core dumped)
> GTester: last random seed: R02S9569aabcb2d834a9dadcce272c5588db
>
> so the test is definitely triggering the problem as patched by part 1. 
> Although I'm not confident enough of what the test is doing for an 
> R-b, and would like it to be less noisy, I can at least add:
>
> Tested-by: Eric Blake <address@hidden>

Thanks