Commit 313d7b00 authored Nov 24, 2010 by Keir Fraser Committed by Konrad Rzeszutek Wilk Apr 14, 2011

blkback: Fix CVE-2010-3699



A guest can cause the backend driver to leak a kernel thread. Such
leaked threads hold references to the device, whichmakes the device
impossible to tear down. If shut down, the guest remains a zombie
domain, the xenwatch process hangs, and most xm commands will stop
working.

This patch tries to do the following for blkback:
    - identify/extract idempotent teardown operations,
    - add/move the invocation of said teardown operation
      right before we're about to allocate new resources in the
      Connected states.

[ linux-2.6.18-xen.hg 59f097ef181b ]

Signed-off-by: Laszlo Ersek <lersek@redhat.com>
Signed-off-by: Keir Fraser <keir@xen.org>
Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>

parent a81135d9

drivers/xen/blkback/xenbus.c

+6 −0

Original line number	Diff line number	Diff line
		@@ -382,6 +382,11 @@ static void frontend_changed(struct xenbus_device *dev,
		if (dev->state == XenbusStateConnected)
		break;

		/* Enforce precondition before potential leak point.
		* blkif_disconnect() is idempotent.
		*/
		blkif_disconnect(be->blkif);

		err = connect_ring(be);
		if (err)
		break;
		@@ -399,6 +404,7 @@ static void frontend_changed(struct xenbus_device *dev,
		break;
		/* fall through if not online */
		case XenbusStateUnknown:
		/* implies blkif_disconnect() via blkback_remove() */
		device_unregister(&dev->dev);
		break;