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hw/virtio: check owner for removing objects

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Shared objects lack spoofing protection.
For VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE messages
received by the vhost-user interface, any backend was
allowed to remove entries from the shared table just
by knowing the UUID. Only the owner of the entry
shall be allowed to removed their resources
from the table.

To fix that, add a check for all
*SHARED_OBJECT_REMOVE messages received.
A vhost device can only remove TYPE_VHOST_DEV
entries that are owned by them, otherwise skip
the removal, and inform the device that the entry
has not been removed in the answer.

Signed-off-by: Albert Esteve <aesteve@redhat.com>
Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20240219143423.272012-2-aesteve@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Reviewed-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
Albert Esteve 2024-02-19 15:34:19 +01:00 committed by Michael S. Tsirkin
parent 633487df8d
commit 043e127a12
2 changed files with 22 additions and 3 deletions
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4
docs/interop/vhost-user.rst
View File

@ -1839,7 +1839,9 @@ is sent by the front-end.
When the ``VHOST_USER_PROTOCOL_F_SHARED_OBJECT`` protocol
feature has been successfully negotiated, this message can be submitted
by the backend to remove themselves from to the virtio-dmabuf shared
table API. The shared table will remove the back-end device associated with
table API. Only the back-end owning the entry (i.e., the one that first added
it) will have permission to remove it. Otherwise, the message is ignored.
The shared table will remove the back-end device associated with
the UUID. If ``VHOST_USER_PROTOCOL_F_REPLY_ACK`` is negotiated, and the
back-end sets the ``VHOST_USER_NEED_REPLY`` flag, the front-end must respond
with zero when operation is successfully completed, or non-zero otherwise.

21
hw/virtio/vhost-user.c
View File

@ -1611,11 +1611,27 @@ vhost_user_backend_handle_shared_object_add(struct vhost_dev *dev,
}
static int
vhost_user_backend_handle_shared_object_remove(VhostUserShared *object)
vhost_user_backend_handle_shared_object_remove(struct vhost_dev *dev,
VhostUserShared *object)
{
QemuUUID uuid;
memcpy(uuid.data, object->uuid, sizeof(object->uuid));
switch (virtio_object_type(&uuid)) {
case TYPE_VHOST_DEV:
{
struct vhost_dev *owner = virtio_lookup_vhost_device(&uuid);
if (dev != owner) {
/* Not allowed to remove non-owned entries */
return 0;
}
break;
}
default:
/* Not allowed to remove non-owned entries */
return 0;
}
return virtio_remove_resource(&uuid);
}
@ -1794,7 +1810,8 @@ static gboolean backend_read(QIOChannel *ioc, GIOCondition condition,
ret = vhost_user_backend_handle_shared_object_add(dev, &payload.object);
break;
case VHOST_USER_BACKEND_SHARED_OBJECT_REMOVE:
ret = vhost_user_backend_handle_shared_object_remove(&payload.object);
ret = vhost_user_backend_handle_shared_object_remove(dev,
&payload.object);
break;
case VHOST_USER_BACKEND_SHARED_OBJECT_LOOKUP:
ret = vhost_user_backend_handle_shared_object_lookup(dev->opaque, ioc,