From 7157e2e23e89adcd436caeab31fdd6b47eded377 Mon Sep 17 00:00:00 2001 From: Stefan Hajnoczi Date: Sun, 8 May 2011 22:29:07 +0100 Subject: [PATCH] virtio: guard against negative vq notifies The virtio_queue_notify() function checks that the virtqueue number is less than the maximum number of virtqueues. A signed comparison is used but the virtqueue number could be negative if a buggy or malicious guest is run. This results in memory accesses outside of the virtqueue array. It is risky doing input validation in common code instead of at the guest<->host boundary. Note that virtio_queue_set_addr(), virtio_queue_get_addr(), virtio_queue_get_num(), and many other virtio functions do *not* validate the virtqueue number argument. Instead of fixing the comparison in virtio_queue_notify(), move the comparison to the virtio bindings (just like VIRTIO_PCI_QUEUE_SEL) where we have a uint32_t value and can avoid ever calling into common virtio code if the virtqueue number is invalid. Signed-off-by: Stefan Hajnoczi Signed-off-by: Michael S. Tsirkin --- hw/syborg_virtio.c | 4 +++- hw/virtio-pci.c | 4 +++- hw/virtio.c | 4 +--- 3 files changed, 7 insertions(+), 5 deletions(-) diff --git a/hw/syborg_virtio.c b/hw/syborg_virtio.c index 2f3e6da4e..00c7be8c8 100644 --- a/hw/syborg_virtio.c +++ b/hw/syborg_virtio.c @@ -146,7 +146,9 @@ static void syborg_virtio_writel(void *opaque, target_phys_addr_t offset, vdev->queue_sel = value; break; case SYBORG_VIRTIO_QUEUE_NOTIFY: - virtio_queue_notify(vdev, value); + if (value < VIRTIO_PCI_QUEUE_MAX) { + virtio_queue_notify(vdev, value); + } break; case SYBORG_VIRTIO_STATUS: virtio_set_status(vdev, value & 0xFF); diff --git a/hw/virtio-pci.c b/hw/virtio-pci.c index 270e2c743..b86c44162 100644 --- a/hw/virtio-pci.c +++ b/hw/virtio-pci.c @@ -348,7 +348,9 @@ static void virtio_ioport_write(void *opaque, uint32_t addr, uint32_t val) vdev->queue_sel = val; break; case VIRTIO_PCI_QUEUE_NOTIFY: - virtio_queue_notify(vdev, val); + if (val < VIRTIO_PCI_QUEUE_MAX) { + virtio_queue_notify(vdev, val); + } break; case VIRTIO_PCI_STATUS: if (!(val & VIRTIO_CONFIG_S_DRIVER_OK)) { diff --git a/hw/virtio.c b/hw/virtio.c index 6e8814cb6..a6518606c 100644 --- a/hw/virtio.c +++ b/hw/virtio.c @@ -585,9 +585,7 @@ void virtio_queue_notify_vq(VirtQueue *vq) void virtio_queue_notify(VirtIODevice *vdev, int n) { - if (n < VIRTIO_PCI_QUEUE_MAX) { - virtio_queue_notify_vq(&vdev->vq[n]); - } + virtio_queue_notify_vq(&vdev->vq[n]); } uint16_t virtio_queue_vector(VirtIODevice *vdev, int n)