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virtio: stop virtqueue processing if device is broken 

QEMU prints an error message and exits when the device enters an invalid
state.  Terminating the process is heavy-handed.  The guest may still be
able to function even if there is a bug in a virtio guest driver.

Moreover, exiting is a bug in nested virtualization where a nested guest
could DoS other nested guests by killing a pass-through virtio device.
I don't think this configuration is possible today but it is likely in
the future.

If the broken flag is set, do not process virtqueues or write back used
descriptors.  The broken flag can be cleared again by resetting the
device.

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Cornelia Huck <cornelia.huck@de.ibm.com>
This commit is contained in:
Stefan Hajnoczi 2016-09-21 16:52:19 +01:00 committed by Michael S. Tsirkin
parent 8275e2f6be
commit f5ed36635d
2 changed files with 42 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

39
hw/virtio/virtio.c
View File

@ -303,6 +303,10 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
virtqueue_unmap_sg(vq, elem, len);
if (unlikely(vq->vdev->broken)) {
return;
}
idx = (idx + vq->used_idx) % vq->vring.num;
uelem.id = elem->index;
@ -313,6 +317,12 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem,
void virtqueue_flush(VirtQueue *vq, unsigned int count)
{
uint16_t old, new;
if (unlikely(vq->vdev->broken)) {
vq->inuse -= count;
return;
}
/* Make sure buffer is written before we update index. */
smp_wmb();
trace_virtqueue_flush(vq, count);
@ -583,6 +593,9 @@ void *virtqueue_pop(VirtQueue *vq, size_t sz)
struct iovec iov[VIRTQUEUE_MAX_SIZE];
VRingDesc desc;
if (unlikely(vdev->broken)) {
return NULL;
}
if (virtio_queue_empty(vq)) {
return NULL;
}
@ -747,6 +760,10 @@ static void virtio_notify_vector(VirtIODevice *vdev, uint16_t vector)
BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
if (unlikely(vdev->broken)) {
return;
}
if (k->notify) {
k->notify(qbus->parent, vector);
}
@ -830,6 +847,7 @@ void virtio_reset(void *opaque)
k->reset(vdev);
}
vdev->broken = false;
vdev->guest_features = 0;
vdev->queue_sel = 0;
vdev->status = 0;
@ -1137,6 +1155,10 @@ static void virtio_queue_notify_vq(VirtQueue *vq)
if (vq->vring.desc && vq->handle_output) {
VirtIODevice *vdev = vq->vdev;
if (unlikely(vdev->broken)) {
return;
}
trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
vq->handle_output(vdev, vq);
}
@ -1758,6 +1780,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
vdev->config_vector = VIRTIO_NO_VECTOR;
vdev->vq = g_malloc0(sizeof(VirtQueue) * VIRTIO_QUEUE_MAX);
vdev->vm_running = runstate_is_running();
vdev->broken = false;
for (i = 0; i < VIRTIO_QUEUE_MAX; i++) {
vdev->vq[i].vector = VIRTIO_NO_VECTOR;
vdev->vq[i].vdev = vdev;
@ -1944,6 +1967,22 @@ void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name)
vdev->bus_name = g_strdup(bus_name);
}
void GCC_FMT_ATTR(2, 3) virtio_error(VirtIODevice *vdev, const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
error_vreport(fmt, ap);
va_end(ap);
vdev->broken = true;
if (virtio_vdev_has_feature(vdev, VIRTIO_F_VERSION_1)) {
virtio_set_status(vdev, vdev->status | VIRTIO_CONFIG_S_NEEDS_RESET);
virtio_notify_config(vdev);
}
}
static void virtio_device_realize(DeviceState *dev, Error **errp)
{
VirtIODevice *vdev = VIRTIO_DEVICE(dev);

3
include/hw/virtio/virtio.h
View File

@ -87,6 +87,7 @@ struct VirtIODevice
VirtQueue *vq;
uint16_t device_id;
bool vm_running;
bool broken; /* device in invalid state, needs reset */
VMChangeStateEntry *vmstate;
char *bus_name;
uint8_t device_endian;
@ -135,6 +136,8 @@ void virtio_init(VirtIODevice *vdev, const char *name,
uint16_t device_id, size_t config_size);
void virtio_cleanup(VirtIODevice *vdev);
void virtio_error(VirtIODevice *vdev, const char *fmt, ...) GCC_FMT_ATTR(2, 3);
/* Set the child bus name. */
void virtio_device_set_child_bus_name(VirtIODevice *vdev, char *bus_name);