Re: [PATCH-for-9.0 3/4] hw/char/virtio-serial-bus: Protect from DMA re-entrancy bugs

[Michael S. Tsirkin]

On Mon, Apr 08, 2024 at 01:04:11PM +0200, Philippe Mathieu-Daudé wrote:
> On 8/4/24 12:08, Michael S. Tsirkin wrote:
> > On Mon, Apr 08, 2024 at 09:14:39AM +0200, Philippe Mathieu-Daudé wrote:
> > > On 4/4/24 21:13, Philippe Mathieu-Daudé wrote:
> > > > Replace qemu_bh_new_guarded() by virtio_bh_new_guarded()
> > > > so the bus and device use the same guard. Otherwise the
> > > > DMA-reentrancy protection can be bypassed.
> > > > 
> > > > Cc: qemu-stable@nongnu.org
> > > > Suggested-by: Alexander Bulekov <alxndr@bu.edu>
> > > > Signed-off-by: Philippe Mathieu-Daudé <philmd@linaro.org>
> > > > ---
> > > >    hw/char/virtio-serial-bus.c | 3 +--
> > > >    1 file changed, 1 insertion(+), 2 deletions(-)
> > > > 
> > > > diff --git a/hw/char/virtio-serial-bus.c b/hw/char/virtio-serial-bus.c
> > > > index 016aba6374..cd0e3a11f7 100644
> > > > --- a/hw/char/virtio-serial-bus.c
> > > > +++ b/hw/char/virtio-serial-bus.c
> > > > @@ -985,8 +985,7 @@ static void virtser_port_device_realize(DeviceState 
> > > > *dev, Error **errp)
> > > >            return;
> > > >        }
> > > > -    port->bh = qemu_bh_new_guarded(flush_queued_data_bh, port,
> > > > -                                   &dev->mem_reentrancy_guard);
> > > > +    port->bh = virtio_bh_new_guarded(vdev, flush_queued_data_bh, port);
> > > 
> > > Missing:
> > > -- >8 --
> > > -    port->bh = virtio_bh_new_guarded(vdev, flush_queued_data_bh, port);
> > > +    port->bh = virtio_bh_new_guarded(VIRTIO_DEVICE(dev),
> > > +                                     flush_queued_data_bh, port);
> > > ---
> > 
> > I don't get it. vdev is already the correct type. Why do you need
> > VIRTIO_DEVICE here?
> 
> This function doesn't declare vdev.
> 
> > 
> > > >        port->elem = NULL;
> > > >    }
> > 



But it seems clear it wasn't really tested, right?
Philipe here's my ack:

Acked-by: Michael S. Tsirkin <mst@redhat.com>

Feel free to merge these after testing.

-- 
MST