Linux Virtualization - Mar 2014 - [PATCH net] vhost: validate vhost_get_vq_desc return value

vhost fails to validate negative error code
from vhost_get_vq_desc causing
a crash: we are using -EFAULT which is 0xfffffff2
as vector size, which exceeds the allocated size.

The code in question was introduced in commit
8dd014adfea6f173c1ef6378f7e5e7924866c923
    vhost-net: mergeable buffers support

CVE-2014-0055

Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
---

This is needed in -stable.

 drivers/vhost/net.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 026be58..e1e22e0 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -505,9 +505,13 @@ static int get_rx_bufs(struct vhost_virtqueue *vq,
 			r = -ENOBUFS;
 			goto err;
 		}
-		d = vhost_get_vq_desc(vq->dev, vq, vq->iov + seg,
+		r = vhost_get_vq_desc(vq->dev, vq, vq->iov + seg,
 				      ARRAY_SIZE(vq->iov) - seg, &out,
 				      &in, log, log_num);
+		if (unlikely(r < 0))
+			goto err;
+
+		d = r;
 		if (d == vq->num) {
 			r = 0;
 			goto err;
-- 
MST

From: "Michael S. Tsirkin" <mst at redhat.com>
Date: Thu, 27 Mar 2014 12:53:37 +0200
> vhost fails to validate negative error code
> from vhost_get_vq_desc causing
> a crash: we are using -EFAULT which is 0xfffffff2
> as vector size, which exceeds the allocated size.
> 
> The code in question was introduced in commit
> 8dd014adfea6f173c1ef6378f7e5e7924866c923
>     vhost-net: mergeable buffers support
> 
> CVE-2014-0055
> 
> Signed-off-by: Michael S. Tsirkin <mst at redhat.com>
> ---
> 
> This is needed in -stable.
Applied and queued up for -stable, thanks Michael.