qemu: CVE-2017-17381

The Virtio Vring implementation in QEMU allows local OS guest users to
cause a denial of service (divide-by-zero error and QEMU process crash)
by unsetting vring alignment while updating Virtio rings.

Reference:
https://nvd.nist.gov/vuln/detail/CVE-2017-17381

Upstream patch:
https://git.qemu.org/?p=qemu.git;a=commitdiff;h=758ead31c7e17bf17a9ef2e0ca1c3e86ab296b43

(From OE-Core rev: 92a0513837182e2e9aa6c7d4958e495f4b5b4c47)

Signed-off-by: Catalin Enache <catalin.enache@windriver.com>
Signed-off-by: Ross Burton <ross.burton@intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 72 insertions, 0 deletions

diff --git a/meta/recipes-devtools/qemu/qemu/CVE-2017-17381.patch b/meta/recipes-devtools/qemu/qemu/CVE-2017-17381.patch
new file mode 100644
index 0000000000..416771cdcb
--- /dev/null
+++ b/meta/recipes-devtools/qemu/qemu/CVE-2017-17381.patch
@@ -0,0 +1,72 @@
+From 758ead31c7e17bf17a9ef2e0ca1c3e86ab296b43 Mon Sep 17 00:00:00 2001
+From: Prasad J Pandit <pjp@fedoraproject.org>
+Date: Wed, 29 Nov 2017 23:14:27 +0530
+Subject: [PATCH] virtio: check VirtQueue Vring object is set
+
+A guest could attempt to use an uninitialised VirtQueue object
+or unset Vring.align leading to a arithmetic exception. Add check
+to avoid it.
+
+Upstream-Status: Backport
+CVE: CVE-2017-17381
+
+Reported-by: Zhangboxian <zhangboxian@huawei.com>
+Signed-off-by: Prasad J Pandit <pjp@fedoraproject.org>
+Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
+Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
+Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
+Reviewed-by: Cornelia Huck <cohuck@redhat.com>
+Signed-off-by: Catalin Enache <catalin.enache@windriver.com>
+---
+ hw/virtio/virtio.c | 14 +++++++++++---
+ 1 file changed, 11 insertions(+), 3 deletions(-)
+
+diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
+index 703e672..ad564b0 100644
+--- a/hw/virtio/virtio.c
++++ b/hw/virtio/virtio.c
+@@ -182,7 +182,7 @@ void virtio_queue_update_rings(VirtIODevice *vdev, int n)
+ {
+     VRing *vring = &vdev->vq[n].vring;
+ 
+-    if (!vring->desc) {
++    if (!vring->num || !vring->desc || !vring->align) {
+         /* not yet setup -> nothing to do */
+         return;
+     }
+@@ -1414,6 +1414,9 @@ void virtio_config_modern_writel(VirtIODevice *vdev,
+ 
+ void virtio_queue_set_addr(VirtIODevice *vdev, int n, hwaddr addr)
+ {
++    if (!vdev->vq[n].vring.num) {
++        return;
++    }
+     vdev->vq[n].vring.desc = addr;
+     virtio_queue_update_rings(vdev, n);
+ }
+@@ -1426,6 +1429,9 @@ hwaddr virtio_queue_get_addr(VirtIODevice *vdev, int n)
+ void virtio_queue_set_rings(VirtIODevice *vdev, int n, hwaddr desc,
+                             hwaddr avail, hwaddr used)
+ {
++    if (!vdev->vq[n].vring.num) {
++        return;
++    }
+     vdev->vq[n].vring.desc = desc;
+     vdev->vq[n].vring.avail = avail;
+     vdev->vq[n].vring.used = used;
+@@ -1494,8 +1500,10 @@ void virtio_queue_set_align(VirtIODevice *vdev, int n, int align)
+      */
+     assert(k->has_variable_vring_alignment);
+ 
+-    vdev->vq[n].vring.align = align;
+-    virtio_queue_update_rings(vdev, n);
++    if (align) {
++        vdev->vq[n].vring.align = align;
++        virtio_queue_update_rings(vdev, n);
++    }
+ }
+ 
+ static bool virtio_queue_notify_aio_vq(VirtQueue *vq)
+-- 
+2.10.2
+