From 9142072649d593acbd118e71f5d257bd9996ab36 Mon Sep 17 00:00:00 2001
From: eperezma <eperezma@redhat.com>
Date: Fri, 19 Feb 2021 08:49:50 -0300
Subject: [PATCH 12/54] vhost: Check for valid vdev in
 vhost_backend_handle_iotlb_msg
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

RH-Author: eperezma <eperezma@redhat.com>
Message-id: <20210219084950.2159701-1-eperezma@redhat.com>
Patchwork-id: 101110
O-Subject: [RHEL-AV-8.4.0 qemu-kvm PATCH] vhost: Check for valid vdev in vhost_backend_handle_iotlb_msg
Bugzilla: 1880299
RH-Acked-by: Peter Xu <peterx@redhat.com>
RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>
RH-Acked-by: Xiao Wang <jasowang@redhat.com>

BZ: https://bugzilla.redhat.com/show_bug.cgi?id=1880299
BRANCH: rhel-av-8.4.0
UPSTREAM: Merged
BREW: https://brewweb.engineering.redhat.com/brew/taskinfo?taskID=35031170

Not checking this can lead to invalid dev->vdev member access in
vhost_device_iotlb_miss if backend issue an iotlb message in a bad
timing, either maliciously or by a bug.

Reproduced rebooting a guest with testpmd in txonly forward mode.
 #0  0x0000559ffff94394 in vhost_device_iotlb_miss (
     dev=dev@entry=0x55a0012f6680, iova=10245279744, write=1)
     at ../hw/virtio/vhost.c:1013
 #1  0x0000559ffff9ac31 in vhost_backend_handle_iotlb_msg (
     imsg=0x7ffddcfd32c0, dev=0x55a0012f6680)
     at ../hw/virtio/vhost-backend.c:411
 #2  vhost_backend_handle_iotlb_msg (dev=dev@entry=0x55a0012f6680,
     imsg=imsg@entry=0x7ffddcfd32c0)
     at ../hw/virtio/vhost-backend.c:404
 #3  0x0000559fffeded7b in slave_read (opaque=0x55a0012f6680)
     at ../hw/virtio/vhost-user.c:1464
 #4  0x000055a0000c541b in aio_dispatch_handler (
     ctx=ctx@entry=0x55a0010a2120, node=0x55a0012d9e00)
     at ../util/aio-posix.c:329

Fixes: 020e571b8b ("vhost: rework IOTLB messaging")
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Message-Id: <20210129090728.831208-1-eperezma@redhat.com>
Acked-by: Jason Wang <jasowang@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
(cherry picked from commit 4d1ccc17f40f73313e13c84914f70ec3d40ac738)
Signed-off-by: Eugenio Pérez <eperezma@redhat.com>
Signed-off-by: Eduardo Lima (Etrunko) <etrunko@redhat.com>
---
 hw/virtio/vhost-backend.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/hw/virtio/vhost-backend.c b/hw/virtio/vhost-backend.c
index 222bbcc62d..31b33bde37 100644
--- a/hw/virtio/vhost-backend.c
+++ b/hw/virtio/vhost-backend.c
@@ -406,6 +406,11 @@ int vhost_backend_handle_iotlb_msg(struct vhost_dev *dev,
 {
     int ret = 0;
 
+    if (unlikely(!dev->vdev)) {
+        error_report("Unexpected IOTLB message when virtio device is stopped");
+        return -EINVAL;
+    }
+
     switch (imsg->type) {
     case VHOST_IOTLB_MISS:
         ret = vhost_device_iotlb_miss(dev, imsg->iova,
-- 
2.27.0