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[Qemu-devel] [PATCH] virtio: guard against negative vq notifies
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [PATCH] virtio: guard against negative vq notifies |
Date: |
Sun, 8 May 2011 22:29:07 +0100 |
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 <address@hidden>
---
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 2f3e6da..00c7be8 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 c19629d..6862aa7 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 6e8814c..a651860 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)
--
1.7.4.4
- [Qemu-devel] [PATCH] virtio: guard against negative vq notifies,
Stefan Hajnoczi <=