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From 612017cc4834cd5eabc12afc7dd6cebf890b42e5 Mon Sep 17 00:00:00 2001
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From: Xiao Wang <jasowang@redhat.com>
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Date: Fri, 19 Aug 2016 09:24:25 +0200
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Subject: [PATCH] virtio: validate the existence of handle_output before
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 calling it
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RH-Author: Xiao Wang <jasowang@redhat.com>
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Message-id: <1471598665-23846-1-git-send-email-jasowang@redhat.com>
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Patchwork-id: 72021
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O-Subject: [RHEL7.3 qemu-kvm PATCH] virtio: validate the existence of handle_output before calling it
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Bugzilla: 1367040
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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RH-Acked-by: Pankaj Gupta <pagupta@redhat.com>
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Bugzilla: 1367040
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Brew Build: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=11620539
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Test status: Tested by myself.
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We don't validate the existence of handle_output which may let a buggy
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guest to trigger a SIGSEV easily. E.g:
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1) write 10 to queue_sel to a virtio net device with only 1 queue
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2) setup an arbitrary pfn
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3) then notify queue 10
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Fixing this by validating the existence of handle_output before.
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Cc: qemu-stable@nongnu.org
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Cc: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Jason Wang <jasowang@redhat.com>
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Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
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Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
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Reviewed-by: Don Koch <dkoch@verizon.com>
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Reviewed-by: Fam Zheng <famz@redhat.com>
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(cherry picked from commit 9e0f5b8108e248b78444c9a2ec41a8309825736c)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 hw/virtio/virtio.c | 3 ++-
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 1 file changed, 2 insertions(+), 1 deletion(-)
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diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
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index a861870..e67337b 100644
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--- a/hw/virtio/virtio.c
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+++ b/hw/virtio/virtio.c
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@@ -692,8 +692,9 @@ int virtio_queue_get_id(VirtQueue *vq)
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 void virtio_queue_notify_vq(VirtQueue *vq)
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 {
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-    if (vq->vring.desc) {
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+    if (vq->vring.desc && vq->handle_output) {
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         VirtIODevice *vdev = vq->vdev;
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+
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         trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
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         vq->handle_output(vdev, vq);
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     }
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-- 
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1.8.3.1
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