| Message ID | 20201028134643.110698-1-felipe@nutanix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [v2] virtio: skip guest index check on device load | expand |
On 2020/10/28 下午9:47, Felipe Franciosi wrote: > QEMU must be careful when loading device state off migration streams to > prevent a malicious source from exploiting the emulator. Overdoing these > checks has the side effect of allowing a guest to "pin itself" in cloud > environments by messing with state which is entirely in its control. > > Similarly to what f3081539 achieved in usb_device_post_load(), this > commit removes such a check from virtio_load(). Worth noting, the result > of a load without this check is the same as if a guest enables a VQ with > invalid indexes to begin with. That is, the virtual device is set in a > broken state (by the datapath handler) and must be reset. > > Signed-off-by: Felipe Franciosi <felipe@nutanix.com> > --- > v2: Keep the check around for logging. > > hw/virtio/virtio.c | 13 +++++++------ > 1 file changed, 7 insertions(+), 6 deletions(-) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 6f8f865aff..ceb58fda6c 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -17,6 +17,7 @@ > #include "trace.h" > #include "exec/address-spaces.h" > #include "qemu/error-report.h" > +#include "qemu/log.h" > #include "qemu/main-loop.h" > #include "qemu/module.h" > #include "hw/virtio/virtio.h" > @@ -3160,12 +3161,12 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) > nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx; > /* Check it isn't doing strange things with descriptor numbers. */ > if (nheads > vdev->vq[i].vring.num) { > - error_report("VQ %d size 0x%x Guest index 0x%x " > - "inconsistent with Host index 0x%x: delta 0x%x", > - i, vdev->vq[i].vring.num, > - vring_avail_idx(&vdev->vq[i]), > - vdev->vq[i].last_avail_idx, nheads); > - return -1; > + qemu_log_mask(LOG_GUEST_ERROR, > + "VQ %d size 0x%x Guest index 0x%x " > + "inconsistent with Host index 0x%x: delta 0x%x", > + i, vdev->vq[i].vring.num, > + vring_avail_idx(&vdev->vq[i]), > + vdev->vq[i].last_avail_idx, nheads); > } > vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]); > vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]); Acked-by: Jason Wang <jasowang@redhat.com>
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 6f8f865aff..ceb58fda6c 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -17,6 +17,7 @@ #include "trace.h" #include "exec/address-spaces.h" #include "qemu/error-report.h" +#include "qemu/log.h" #include "qemu/main-loop.h" #include "qemu/module.h" #include "hw/virtio/virtio.h" @@ -3160,12 +3161,12 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) nheads = vring_avail_idx(&vdev->vq[i]) - vdev->vq[i].last_avail_idx; /* Check it isn't doing strange things with descriptor numbers. */ if (nheads > vdev->vq[i].vring.num) { - error_report("VQ %d size 0x%x Guest index 0x%x " - "inconsistent with Host index 0x%x: delta 0x%x", - i, vdev->vq[i].vring.num, - vring_avail_idx(&vdev->vq[i]), - vdev->vq[i].last_avail_idx, nheads); - return -1; + qemu_log_mask(LOG_GUEST_ERROR, + "VQ %d size 0x%x Guest index 0x%x " + "inconsistent with Host index 0x%x: delta 0x%x", + i, vdev->vq[i].vring.num, + vring_avail_idx(&vdev->vq[i]), + vdev->vq[i].last_avail_idx, nheads); } vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]); vdev->vq[i].shadow_avail_idx = vring_avail_idx(&vdev->vq[i]);
QEMU must be careful when loading device state off migration streams to prevent a malicious source from exploiting the emulator. Overdoing these checks has the side effect of allowing a guest to "pin itself" in cloud environments by messing with state which is entirely in its control. Similarly to what f3081539 achieved in usb_device_post_load(), this commit removes such a check from virtio_load(). Worth noting, the result of a load without this check is the same as if a guest enables a VQ with invalid indexes to begin with. That is, the virtual device is set in a broken state (by the datapath handler) and must be reset. Signed-off-by: Felipe Franciosi <felipe@nutanix.com> --- v2: Keep the check around for logging. hw/virtio/virtio.c | 13 +++++++------ 1 file changed, 7 insertions(+), 6 deletions(-)