On Fri, Oct 12, 2018 at 09:44:25AM +0200, David Hildenbrand wrote:
> On 12/10/2018 05:24, David Gibson wrote:
> > The virtio-balloon device's verification of the address given to it by the
> > guest has a number of faults:
> > * The addresses here are guest physical addresses, which should be
> > 'hwaddr' rather than 'ram_addr_t' (the distinction is admittedly
> > pretty subtle and confusing)
> > * We don't check for section.mr being NULL, which is the main way that
> > memory_region_find() reports basic failures. We really need to check
> > that before looking at any other section fields, because
> > memory_region_find() doesn't initialize them on the failure path
> > * We're passing a length of '1' to memory_region_find(), but really the
> > guest is requesting that we put the entire page into the balloon,
> > so it makes more sense to call it with BALLOON_PAGE_SIZE
> >
> > Signed-off-by: David Gibson <da...@gibson.dropbear.id.au>
> > ---
> > hw/virtio/virtio-balloon.c | 17 ++++++++++-------
> > 1 file changed, 10 insertions(+), 7 deletions(-)
> >
> > diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c
> > index 6ec4bcf4e1..e8611aab0e 100644
> > --- a/hw/virtio/virtio-balloon.c
> > +++ b/hw/virtio/virtio-balloon.c
> > @@ -221,17 +221,20 @@ static void virtio_balloon_handle_output(VirtIODevice
> > *vdev, VirtQueue *vq)
> > }
> >
> > while (iov_to_buf(elem->out_sg, elem->out_num, offset, &pfn, 4) ==
> > 4) {
> > - ram_addr_t pa;
> > - ram_addr_t addr;
> > + hwaddr pa;
> > + hwaddr addr;
> > int p = virtio_ldl_p(vdev, &pfn);
> >
> > - pa = (ram_addr_t) p << VIRTIO_BALLOON_PFN_SHIFT;
> > + pa = (hwaddr) p << VIRTIO_BALLOON_PFN_SHIFT;
> > offset += 4;
> >
> > - /* FIXME: remove get_system_memory(), but how? */
>
> Should we leave that fixme? (on the other hand, virtio-balloon operates
> on all system mamory, so I also don't really see a way around this ...)
Yeah, I took that out deliberately. Given what this is supposed to be
doing, I can't really see how removing get_system_memory() is either
possible or desirable.
> > - section = memory_region_find(get_system_memory(), pa, 1);
> > - if (!int128_nz(section.size) ||
> > - !memory_region_is_ram(section.mr) ||
> > + section = memory_region_find(get_system_memory(), pa,
> > + BALLOON_PAGE_SIZE);
> > + if (!section.mr) {
> > + trace_virtio_balloon_bad_addr(pa);
> > + continue;
> > + }
> > + if (!memory_region_is_ram(section.mr) ||
> > memory_region_is_rom(section.mr) ||
> > memory_region_is_romd(section.mr)) {
> > trace_virtio_balloon_bad_addr(pa);
> >
>
> Reviewed-by: David Hildenbrand <da...@redhat.com>
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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