From 23260e589e52ec83349f22198eab2331b5a1684e Mon Sep 17 00:00:00 2001 From: Matthew Daley Date: Wed, 25 Sep 2013 12:28:47 +1200 Subject: [PATCH] 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 --- hw/xen_disk.c | 1 + 1 file changed, 1 insertion(+) diff --git a/tools/qemu-xen/hw/xen_disk.c b/tools/qemu-xen/hw/xen_disk.c index a402ac8..1cdfcbc 100644 --- a/tools/qemu-xen/hw/xen_disk.c +++ b/tools/qemu-xen/hw/xen_disk.c @@ -299,6 +299,7 @@ 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; } -- 1.7.10.4