xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

This change “xen/xenbus: Don’t leak memory when unmapping the ring on HVM backend” in Linux kernel is authored by Julien Grall <julien.grall [at] citrix.com> on Mon Aug 10 19:10:38 2015 +0100.

xen/xenbus: Don't leak memory when unmapping the ring on HVM backend

The commit ccc9d90a9a8b5c4ad7e9708ec41f75ff9e98d61d "xenbus_client:
Extend interface to support multi-page ring" removes the call to
free_xenballooned_pages() in xenbus_unmap_ring_vfree_hvm(), leaking a
page for every shared ring.

Only with backends running in HVM domains were affected.

Signed-off-by: Julien Grall <julien.grall@citrix.com>
Cc: <stable@vger.kernel.org>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Reviewed-by: Wei Liu <wei.liu2@citrix.com>
Signed-off-by: David Vrabel <david.vrabel@citrix.com>

This Linux change may have been applied to various maintained Linux releases and you can find Linux releases including commit c22fe51.

There are 4 lines of Linux source code added/deleted in this change. Code changes to Linux kernel are as follows.

 drivers/xen/xenbus/xenbus_client.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/xenbus/xenbus_client.c b/drivers/xen/xenbus/xenbus_client.c
index 9ad3272..e303535 100644
--- a/drivers/xen/xenbus/xenbus_client.c
+++ b/drivers/xen/xenbus/xenbus_client.c
@@ -814,8 +814,10 @@ static int xenbus_unmap_ring_vfree_hvm(struct xenbus_device *dev, void *vaddr)
 	rv = xenbus_unmap_ring(dev, node->handles, node->nr_handles,
-	if (!rv)
+	if (!rv) {
+		free_xenballooned_pages(node->nr_handles, node->hvm.pages);
+	}
 		WARN(1, "Leaking %p, size %u page(s)n", vaddr,

The commit for this change in Linux stable tree is c22fe51 (patch).

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