From: Michael S. Tsirkin <mst@redhat.com>
Date: Wed, 4 Mar 2015 16:44:22 +0000 (+0000)
Subject: virtio: validate num_sg when mapping
X-Git-Url: http://xenbits.xensource.com/gitweb?a=commitdiff_plain;h=f25df9882827c8e488fe3f36cc7796b99302391b;p=qemu-upstream-4.2-testing.git

virtio: validate num_sg when mapping

CVE-2013-4535
CVE-2013-4536

Both virtio-block and virtio-serial read,
VirtQueueElements are read in as buffers, and passed to
virtqueue_map_sg(), where num_sg is taken from the wire and can force
writes to indicies beyond VIRTQUEUE_MAX_SIZE.

To fix, validate num_sg.

Reported-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: Amit Shah <amit.shah@redhat.com>
Signed-off-by: Juan Quintela <quintela@redhat.com>
Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
---

diff --git a/hw/virtio.c b/hw/virtio.c
index e1365a3f7..068c24dc1 100644
--- a/hw/virtio.c
+++ b/hw/virtio.c
@@ -396,6 +396,12 @@ void virtqueue_map_sg(struct iovec *sg, target_phys_addr_t *addr,
     unsigned int i;
     target_phys_addr_t len;
 
+    if (num_sg >= VIRTQUEUE_MAX_SIZE) {
+        error_report("virtio: map attempt out of bounds: %zd > %d",
+                     num_sg, VIRTQUEUE_MAX_SIZE);
+        exit(1);
+    }
+
     for (i = 0; i < num_sg; i++) {
         len = sg[i].iov_len;
         sg[i].iov_base = cpu_physical_memory_map(addr[i], &len, is_write);