Re: [PATCH] vhost-vsock: delete vqs in vhost_vsock_unrealize to avoid memleaks

[Stefano Garzarella]

On Tue, Jan 14, 2020 at 5:45 PM Stefan Hajnoczi <address@hidden> wrote:
>
> On Tue, Jan 14, 2020 at 03:52:29PM +0800, address@hidden wrote:
> > From: Pan Nengyuan <address@hidden>
> >
> > Receive/transmit/event vqs forgot to cleanup in vhost_vsock_unrealize. This
> > patch save receive/transmit vq pointer in realize() and cleanup vqs
> > through those vq pointers in unrealize(). The leak stack is as follow:
> >
> > Direct leak of 21504 byte(s) in 3 object(s) allocated from:
> >   #0 0x7f86a1356970 (/lib64/libasan.so.5+0xef970)  ??:?
> >   #1 0x7f86a09aa49d (/lib64/libglib-2.0.so.0+0x5249d)  ??:?
> >   #2 0x5604852f85ca (./x86_64-softmmu/qemu-system-x86_64+0x2c3e5ca)  
> > /mnt/sdb/qemu/hw/virtio/virtio.c:2333
> >   #3 0x560485356208 (./x86_64-softmmu/qemu-system-x86_64+0x2c9c208)  
> > /mnt/sdb/qemu/hw/virtio/vhost-vsock.c:339
> >   #4 0x560485305a17 (./x86_64-softmmu/qemu-system-x86_64+0x2c4ba17)  
> > /mnt/sdb/qemu/hw/virtio/virtio.c:3531
> >   #5 0x5604858e6b65 (./x86_64-softmmu/qemu-system-x86_64+0x322cb65)  
> > /mnt/sdb/qemu/hw/core/qdev.c:865
> >   #6 0x5604861e6c41 (./x86_64-softmmu/qemu-system-x86_64+0x3b2cc41)  
> > /mnt/sdb/qemu/qom/object.c:2102
> >
> > Reported-by: Euler Robot <address@hidden>
> > Signed-off-by: Pan Nengyuan <address@hidden>
> > ---
> >  hw/virtio/vhost-vsock.c         | 9 +++++++--
> >  include/hw/virtio/vhost-vsock.h | 2 ++
> >  2 files changed, 9 insertions(+), 2 deletions(-)
> >
> > diff --git a/hw/virtio/vhost-vsock.c b/hw/virtio/vhost-vsock.c
> > index f5744363a8..896c0174c1 100644
> > --- a/hw/virtio/vhost-vsock.c
> > +++ b/hw/virtio/vhost-vsock.c
> > @@ -335,8 +335,10 @@ static void vhost_vsock_device_realize(DeviceState 
> > *dev, Error **errp)
> >                  sizeof(struct virtio_vsock_config));
> >
> >      /* Receive and transmit queues belong to vhost */
> > -    virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE, 
> > vhost_vsock_handle_output);
> > -    virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE, 
> > vhost_vsock_handle_output);
> > +    vsock->recv_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
> > +                                      vhost_vsock_handle_output);
> > +    vsock->trans_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
> > +                                       vhost_vsock_handle_output);
> >
> >      /* The event queue belongs to QEMU */
> >      vsock->event_vq = virtio_add_queue(vdev, VHOST_VSOCK_QUEUE_SIZE,
> > @@ -378,6 +380,9 @@ static void vhost_vsock_device_unrealize(DeviceState 
> > *dev, Error **errp)
> >      /* This will stop vhost backend if appropriate. */
> >      vhost_vsock_set_status(vdev, 0);
> >
> > +    virtio_delete_queue(vsock->recv_vq);
> > +    virtio_delete_queue(vsock->trans_vq);
> > +    virtio_delete_queue(vsock->event_vq);
> >      vhost_dev_cleanup(&vsock->vhost_dev);
> >      virtio_cleanup(vdev);
> >  }
>
> Please delete the virtqueues after vhost cleanup (the reverse
> initialization order).  There is currently no reason why it has to be
> done in reverse initialization order, your patch should work too, but
> it's a good default for avoiding user-after-free bugs.
>

Agree!

Since we are here, should we delete the queues also in the error path
of vhost_vsock_device_realize()?

Thanks,
Stefano