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From:   Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To:     linux-kernel@vger.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        stable@vger.kernel.org, "Michael S. Tsirkin" <mst@redhat.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Andrea Arcangeli <aarcange@redhat.com>,
        Jason Wang <jasowang@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.4 099/114] vhost: Fix Spectre V1 vulnerability
Date:   Thu,  8 Nov 2018 13:51:54 -0800
Message-Id: <20181108215109.654652832@linuxfoundation.org>
In-Reply-To: <20181108215059.051093652@linuxfoundation.org>
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4.4-stable review patch.  If anyone has any objections, please let me know.

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

From: Jason Wang <jasowang@redhat.com>

[ Upstream commit ff002269a4ee9c769dbf9365acef633ebcbd6cbe ]

The idx in vhost_vring_ioctl() was controlled by userspace, hence a
potential exploitation of the Spectre variant 1 vulnerability.

Fixing this by sanitizing idx before using it to index d->vqs.

Cc: Michael S. Tsirkin <mst@redhat.com>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Signed-off-by: Jason Wang <jasowang@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/vhost/vhost.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -27,6 +27,7 @@
 #include <linux/cgroup.h>
 #include <linux/module.h>
 #include <linux/sort.h>
+#include <linux/nospec.h>
 
 #include "vhost.h"
 
@@ -748,6 +749,7 @@ long vhost_vring_ioctl(struct vhost_dev
 	if (idx >= d->nvqs)
 		return -ENOBUFS;
 
+	idx = array_index_nospec(idx, d->nvqs);
 	vq = d->vqs[idx];
 
 	mutex_lock(&vq->mutex);