virtio: handle > 2 billion page balloon targets

If the host asks for a huge target towards_target() can overflow, and
we up oops as we try to release more pages than we have.  The simple
fix is to use a 64-bit value.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

1 files changed, 2 insertions, 2 deletions

diff --git a/drivers/virtio/virtio_balloon.c b/drivers/virtio/virtio_balloon.c
index c8a4332d1132..0b3efc31ee6d 100644
--- a/drivers/virtio/virtio_balloon.c
+++ b/drivers/virtio/virtio_balloon.c
@@ -152,7 +152,7 @@ static void virtballoon_changed(struct virtio_device *vdev)
         wake_up(&vb->config_change);
 }
 
-static inline int towards_target(struct virtio_balloon *vb)
+static inline s64 towards_target(struct virtio_balloon *vb)
 {
         u32 v;
         __virtio_config_val(vb->vdev,
@@ -176,7 +176,7 @@ static int balloon(void *_vballoon)
 
         set_freezable();
         while (!kthread_should_stop()) {
-                int diff;
+                s64 diff;
 
                 try_to_freeze();
                 wait_event_interruptible(vb->config_change,