File CVE-2013-4375-xsa71.patch of Package xen

References: bnc#842515 CVE-2013-4375 XSA-71 

xen_disk: mark ioreq as mapped before unmapping in error case

Commit c6961b7d ("xen_disk: use bdrv_aio_flush instead of bdrv_flush")
modified the semantics of ioreq_{un,}map so that they are idempotent if
called when they're not needed (ie., twice in a row). However, it neglected
to handle the case where batch mapping is not being used (the default), and
one of the grants fails to map. In this case, ioreq_unmap will be called to
unwind and unmap any mappings already performed, but ioreq_unmap simply
returns due to the aforementioned change (the ioreq has not already been
marked as mapped).

The frontend user can therefore force xen_disk to leak grant mappings, a
per-backend-domain limited resource.

Fix by marking the ioreq as mapped before calling ioreq_unmap in this
situation.

This is XSA-71 / CVE-2013-4375

Signed-off-by: Matthew Daley <mattjd@gmail.com>

--- a/tools/qemu-xen-dir-remote/hw/xen_disk.c
+++ b/tools/qemu-xen-dir-remote/hw/xen_disk.c
@@ -406,6 +406,7 @@ static int ioreq_map(struct ioreq *ioreq
                 xen_be_printf(&ioreq->blkdev->xendev, 0,
                               "can't map grant ref %d (%s, %d maps)\n",
                               refs[i], strerror(errno), ioreq->blkdev->cnt_map);
+                ioreq->mapped = 1;
                 ioreq_unmap(ioreq);
                 return -1;
             }