virtio_ccw: fix vcdev pointer handling issues

The interrupt handler virtio_ccw_int_handler() using the vcdev pointer
is protected by the ccw_device lock. Resetting the pointer within the
ccw_device structure should be done when holding this lock.

Also resetting the vcdev pointer (under the ccw_device lock) prior to
freeing the vcdev pointer memory removes a critical path.

Signed-off-by: Heinz Graalfs <graalfs@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

1 files changed, 28 insertions, 7 deletions

diff --git a/drivers/s390/kvm/virtio_ccw.c b/drivers/s390/kvm/virtio_ccw.c
index 0fc584832001..413c6304d511 100644
--- a/drivers/s390/kvm/virtio_ccw.c
+++ b/drivers/s390/kvm/virtio_ccw.c
@@ -636,6 +636,8 @@ static void virtio_ccw_int_handler(struct ccw_device *cdev,
         struct virtqueue *vq;
         struct virtio_driver *drv;
 
+        if (!vcdev)
+                return;
         /* Check if it's a notification from the host. */
         if ((intparm == 0) &&
             (scsw_stctl(&irb->scsw) ==
@@ -734,23 +736,37 @@ static int virtio_ccw_probe(struct ccw_device *cdev)
         return 0;
 }
 
+static struct virtio_ccw_device *virtio_grab_drvdata(struct ccw_device *cdev)
+{
+        unsigned long flags;
+        struct virtio_ccw_device *vcdev;
+
+        spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
+        vcdev = dev_get_drvdata(&cdev->dev);
+        if (!vcdev) {
+                spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+                return NULL;
+        }
+        dev_set_drvdata(&cdev->dev, NULL);
+        spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
+        return vcdev;
+}
+
 static void virtio_ccw_remove(struct ccw_device *cdev)
 {
-        struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
+        struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);
 
-        if (cdev->online) {
+        if (vcdev && cdev->online)
                 unregister_virtio_device(&vcdev->vdev);
-                dev_set_drvdata(&cdev->dev, NULL);
-        }
         cdev->handler = NULL;
 }
 
 static int virtio_ccw_offline(struct ccw_device *cdev)
 {
-        struct virtio_ccw_device *vcdev = dev_get_drvdata(&cdev->dev);
+        struct virtio_ccw_device *vcdev = virtio_grab_drvdata(cdev);
 
-        unregister_virtio_device(&vcdev->vdev);
-        dev_set_drvdata(&cdev->dev, NULL);
+        if (vcdev)
+                unregister_virtio_device(&vcdev->vdev);
         return 0;
 }
 
@@ -759,6 +775,7 @@ static int virtio_ccw_online(struct ccw_device *cdev)
 {
         int ret;
         struct virtio_ccw_device *vcdev;
+        unsigned long flags;
 
         vcdev = kzalloc(sizeof(*vcdev), GFP_KERNEL);
         if (!vcdev) {
@@ -786,7 +803,9 @@ static int virtio_ccw_online(struct ccw_device *cdev)
         INIT_LIST_HEAD(&vcdev->virtqueues);
         spin_lock_init(&vcdev->lock);
 
+        spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
         dev_set_drvdata(&cdev->dev, vcdev);
+        spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
         vcdev->vdev.id.vendor = cdev->id.cu_type;
         vcdev->vdev.id.device = cdev->id.cu_model;
         ret = register_virtio_device(&vcdev->vdev);
@@ -797,7 +816,9 @@ static int virtio_ccw_online(struct ccw_device *cdev)
         }
         return 0;
 out_put:
+        spin_lock_irqsave(get_ccwdev_lock(cdev), flags);
         dev_set_drvdata(&cdev->dev, NULL);
+        spin_unlock_irqrestore(get_ccwdev_lock(cdev), flags);
         put_device(&vcdev->vdev.dev);
         return ret;
 out_free: