[PATCH v2 1/2] vhost: release memory_listener object in error path

[P J P <ppandit@redhat.com>]

From: Prasad Pandit <pjp@fedoraproject.org>

vhost_dev_start function does not release memory_listener object
in case of an error. This may crash the guest when vhost is unable
to set memory table:

  stack trace of thread 125653:
  Program terminated with signal SIGSEGV, Segmentation fault
  #0  memory_listener_register (qemu-kvm + 0x6cda0f)
  #1  vhost_dev_start (qemu-kvm + 0x699301)
  #2  vhost_net_start (qemu-kvm + 0x45b03f)
  #3  virtio_net_set_status (qemu-kvm + 0x665672)
  #4  qmp_set_link (qemu-kvm + 0x548fd5)
  #5  net_vhost_user_event (qemu-kvm + 0x552c45)
  #6  tcp_chr_connect (qemu-kvm + 0x88d473)
  #7  tcp_chr_new_client (qemu-kvm + 0x88cf83)
  #8  tcp_chr_accept (qemu-kvm + 0x88b429)
  #9  qio_net_listener_channel_func (qemu-kvm + 0x7ac07c)
  #10 g_main_context_dispatch (libglib-2.0.so.0 + 0x54e2f)

Release memory_listener objects in the error path.

Signed-off-by: Prasad Pandit <pjp@fedoraproject.org>
---
 hw/virtio/vhost.c | 3 +++
 1 file changed, 3 insertions(+)

v2: split a single patch into two. Mention about vhost set mem table failure
resulting in guest crash.

diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 23da579ce2..6be4a0626a 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -2004,6 +2004,9 @@ fail_vq:
     }

 fail_mem:
+    if (vhost_dev_has_iommu(hdev)) {
+        memory_listener_unregister(&hdev->iommu_listener);
+    }
 fail_features:
     vdev->vhost_started = false;
     hdev->started = false;
--
2.40.1