linux-kernel - [PATCH 3.16 104/129] s390/virtio: handle find on invalid queue gracefully

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Date:   Sun, 07 Jul 2019 17:54:17 +0100
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, Denis Kirjanov <kda@...ux-powerpc.org>,
        "Cornelia Huck" <cohuck@...hat.com>,
        "Michael S. Tsirkin" <mst@...hat.com>,
        "Halil Pasic" <pasic@...ux.ibm.com>
Subject: [PATCH 3.16 104/129] s390/virtio: handle find on invalid queue
 gracefully

3.16.70-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Halil Pasic <pasic@...ux.ibm.com>

commit 3438b2c039b4bf26881786a1f3450f016d66ad11 upstream.

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.

Signed-off-by: Halil Pasic <pasic@...ux.ibm.com>
Signed-off-by: Cornelia Huck <cohuck@...hat.com>
Signed-off-by: Michael S. Tsirkin <mst@...hat.com>
[bwh: Backported to 3.16: adjust filename]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
 drivers/s390/kvm/virtio_ccw.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -258,6 +258,8 @@ 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);
 }
@@ -386,7 +388,7 @@ static int virtio_ccw_read_vq_conf(struc
 	ccw->count = sizeof(struct vq_config_block);
 	ccw->cda = (__u32)(unsigned long)(vcdev->config_block);
 	ccw_io_helper(vcdev, ccw, VIRTIO_CCW_DOING_READ_VQ_CONF);
-	return vcdev->config_block->num;
+	return vcdev->config_block->num ?: -ENOENT;
 }
 
 static void virtio_ccw_del_vq(struct virtqueue *vq, struct ccw1 *ccw)