[ 017/171 ] vhost/net: fix heads usage of ubuf_info

[Steven Rostedt]

3.6.11.2 stable review patch.
If anyone has any objections, please let me know.

------------------

From: "Michael S. Tsirkin" <mst@xxxxxxxxxx>

[ Upstream commit 46aa92d1ba162b4b3d6b7102440e459d4e4ee255 ]

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@xxxxxxxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: stable@xxxxxxxxxx
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
 drivers/vhost/net.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/vhost/net.c b/drivers/vhost/net.c
index 7f93f34..156a360 100644
--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -235,7 +235,8 @@ 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 = len;
 				ubuf->callback = vhost_zerocopy_callback;
-- 
1.7.10.4


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/