On 02/03/2023 11.14, Carlos López wrote:
When a virtqueue size is changed by the guest via virtio_queue_set_num(), its region cache is not automatically updated. If the size was increased, this could lead to accessing the cache out of bounds. For example, in vring_get_used_event():static inline uint16_t vring_get_used_event(VirtQueue *vq) { return vring_avail_ring(vq, vq->vring.num); } static inline uint16_t vring_avail_ring(VirtQueue *vq, int i) { VRingMemoryRegionCaches *caches = vring_get_region_caches(vq); hwaddr pa = offsetof(VRingAvail, ring[i]); if (!caches) { return 0; } return virtio_lduw_phys_cached(vq->vdev, &caches->avail, pa); } vq->vring.num will be greater than caches->avail.len, which will trigger a failed assertion down the call path of virtio_lduw_phys_cached(). Fix this by calling virtio_queue_update_rings() after virtio_queue_set_num() if we are not already calling virtio_queue_set_rings(). Signed-off-by: Carlos López <[email protected]> --- hw/s390x/virtio-ccw.c | 1 + hw/virtio/virtio-mmio.c | 5 ++--- hw/virtio/virtio-pci.c | 1 + 3 files changed, 4 insertions(+), 3 deletions(-) diff --git a/hw/s390x/virtio-ccw.c b/hw/s390x/virtio-ccw.c index e33e5207ab..89891ac58a 100644 --- a/hw/s390x/virtio-ccw.c +++ b/hw/s390x/virtio-ccw.c @@ -237,6 +237,7 @@ static int virtio_ccw_set_vqs(SubchDev *sch, VqInfoBlock *info, return -EINVAL; } virtio_queue_set_num(vdev, index, num); + virtio_queue_update_rings(vdev, index); } else if (virtio_queue_get_num(vdev, index) > num) { /* Fail if we don't have a big enough queue. */ return -EINVAL;
FWIW, s390 part: Acked-by: Thomas Huth <[email protected]>
