linux-kernel - [ 12/72] vhost/net: fix heads usage of ubuf

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Message-Id: <20130326224921.001996044@linuxfoundation.org>
Date:	Tue, 26 Mar 2013 15:50:55 -0700
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	"David S. Miller" <davem@...emloft.net>, stable@...nel.org
Subject: [ 12/72] vhost/net: fix heads usage of ubuf_info

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

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


From: "Michael S. Tsirkin" <mst@...hat.com>

[ 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@...tcorp.com.au>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
Cc: stable@...nel.org
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/vhost/net.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

--- a/drivers/vhost/net.c
+++ b/drivers/vhost/net.c
@@ -235,7 +235,8 @@ static void handle_tx(struct vhost_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;


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