From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([140.186.70.92]:42286) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QJBXY-0001Cw-Uf for qemu-devel@nongnu.org; Sun, 08 May 2011 17:29:25 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QJBXX-0003mE-S0 for qemu-devel@nongnu.org; Sun, 08 May 2011 17:29:24 -0400 Received: from mtagate3.uk.ibm.com ([194.196.100.163]:43717) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QJBXX-0003m3-Gu for qemu-devel@nongnu.org; Sun, 08 May 2011 17:29:23 -0400 Received: from d06nrmr1707.portsmouth.uk.ibm.com (d06nrmr1707.portsmouth.uk.ibm.com [9.149.39.225]) by mtagate3.uk.ibm.com (8.13.1/8.13.1) with ESMTP id p48LTLaM001378 for ; Sun, 8 May 2011 21:29:21 GMT Received: from d06av06.portsmouth.uk.ibm.com (d06av06.portsmouth.uk.ibm.com [9.149.37.217]) by d06nrmr1707.portsmouth.uk.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id p48LUUwg2375912 for ; Sun, 8 May 2011 22:30:36 +0100 Received: from d06av06.portsmouth.uk.ibm.com (loopback [127.0.0.1]) by d06av06.portsmouth.uk.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p48LTE13020869 for ; Sun, 8 May 2011 15:29:14 -0600 From: Stefan Hajnoczi Date: Sun, 8 May 2011 22:29:07 +0100 Message-Id: <1304890147-26679-1-git-send-email-stefanha@linux.vnet.ibm.com> Subject: [Qemu-devel] [PATCH] virtio: guard against negative vq notifies List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: Stefan Hajnoczi , "Michael S. Tsirkin" 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 --- 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