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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,
        syzbot+6304bf97ef436580fede@syzkaller.appspotmail.com,
        Jason Wang <jasowang@redhat.com>,
        "Michael S. Tsirkin" <mst@redhat.com>,
        "David S. Miller" <davem@davemloft.net>
Subject: [PATCH 4.15 164/168] vhost: validate log when IOTLB is enabled
Date:   Wed, 11 Apr 2018 00:25:06 +0200
Message-Id: <20180410212808.207271433@linuxfoundation.org>
In-Reply-To: <20180410212800.144079021@linuxfoundation.org>
References: <20180410212800.144079021@linuxfoundation.org>
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4.15-stable review patch.  If anyone has any objections, please let me know.

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

From: Jason Wang <jasowang@redhat.com>


[ Upstream commit d65026c6c62e7d9616c8ceb5a53b68bcdc050525 ]

Vq log_base is the userspace address of bitmap which has nothing to do
with IOTLB. So it needs to be validated unconditionally otherwise we
may try use 0 as log_base which may lead to pin pages that will lead
unexpected result (e.g trigger BUG_ON() in set_bit_to_user()).

Fixes: 6b1e6cc7855b0 ("vhost: new device IOTLB API")
Reported-by: syzbot+6304bf97ef436580fede@syzkaller.appspotmail.com
Signed-off-by: Jason Wang <jasowang@redhat.com>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 drivers/vhost/vhost.c |   14 ++++++--------
 1 file changed, 6 insertions(+), 8 deletions(-)

--- a/drivers/vhost/vhost.c
+++ b/drivers/vhost/vhost.c
@@ -1256,14 +1256,12 @@ static int vq_log_access_ok(struct vhost
 /* Caller should have vq mutex and device mutex */
 int vhost_vq_access_ok(struct vhost_virtqueue *vq)
 {
-	if (vq->iotlb) {
-		/* When device IOTLB was used, the access validation
-		 * will be validated during prefetching.
-		 */
-		return 1;
-	}
-	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used) &&
-		vq_log_access_ok(vq, vq->log_base);
+	int ret = vq_log_access_ok(vq, vq->log_base);
+
+	if (ret || vq->iotlb)
+		return ret;
+
+	return vq_access_ok(vq, vq->num, vq->desc, vq->avail, vq->used);
 }
 EXPORT_SYMBOL_GPL(vhost_vq_access_ok);