From: Michael S. Tsirkin <mst@redhat.com>
Date: Sun, 17 Mar 2013 02:46:09 +0000 (+0000)
Subject: vhost/net: fix heads usage of ubuf_info
X-Git-Tag: v3.9-rc4~27^2~6
X-Git-Url: http://pileus.org/git/?p=~andy%2Flinux;a=commitdiff_plain;h=46aa92d1ba162b4b3d6b7102440e459d4e4ee255

vhost/net: fix heads usage of ubuf_info

ubuf info allocator uses guest controlled head as an index,
so a malicious guest could put the same head entry in the ring twice,
and we will get two callbacks on the same value.
To fix use upend_idx which is guaranteed to be unique.

Reported-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Cc: stable@kernel.org
Signed-off-by: David S. Miller <davem@davemloft.net>
---

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 959b1cd89e6..ec6fb3fa59b 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -339,7 +339,8 @@ static void handle_tx(struct vhost_net *net)
 				msg.msg_controllen = 0;
 				ubufs = NULL;
 			} else {
-				struct ubuf_info *ubuf = &vq->ubuf_info[head];
+				struct ubuf_info *ubuf;
+				ubuf = vq->ubuf_info + vq->upend_idx;
 
 				vq->heads[vq->upend_idx].len =
 					VHOST_DMA_IN_PROGRESS;