From: Halil Pasic <pasic@linux.ibm.com>
Date: Mon, 21 Jan 2019 13:19:43 +0100
Subject: s390/virtio: handle find on invalid queue gracefully
Git-commit: 3438b2c039b4bf26881786a1f3450f016d66ad11
Patch-mainline: v5.1-rc1
References: bsc#1051510

A queue with a capacity of zero is clearly not a valid virtio queue.
Some emulators report zero queue size if queried with an invalid queue
index. Instead of crashing in this case let us just return -ENOENT. To
make that work properly, let us fix the notifier cleanup logic as well.

Cc: stable@vger.kernel.org
Signed-off-by: Halil Pasic <pasic@linux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@redhat.com>
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Acked-by: Petr Tesarik <ptesarik@suse.com>
---
 drivers/s390/virtio/virtio_ccw.c |    4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/s390/virtio/virtio_ccw.c
+++ b/drivers/s390/virtio/virtio_ccw.c
@@ -275,6 +275,8 @@ static void virtio_ccw_drop_indicators(s
 {
 	struct virtio_ccw_vq_info *info;
 
+	if (!vcdev->airq_info)
+		return;
 	list_for_each_entry(info, &vcdev->virtqueues, node)
 		drop_airq_indicator(info->vq, vcdev->airq_info);
 }
@@ -416,7 +418,7 @@ static int virtio_ccw_read_vq_conf(struc
 	ret = ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_VQ_CONF);
 	if (ret)
 		return ret;
-	return vcdev->config_block->num;
+	return vcdev->config_block->num ?: -ENOENT;
 }
 
 static void virtio_ccw_del_vq(struct virtqueue *vq, struct ccw1 *ccw)