[Xen-changelog] [qemu-upstream-unstable] xen_disk: mark ioreq as mapped before unmapping in error case

[patchbot@xxxxxxx]

commit b97307ecaad98360f41ea36cd9674ef810c4f8cf
Author:     Matthew Daley <mattjd@xxxxxxxxx>
AuthorDate: Thu Oct 10 14:10:48 2013 +0000
Commit:     Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
CommitDate: Thu Oct 10 14:10:48 2013 +0000

    xen_disk: mark ioreq as mapped before unmapping in error case
    
    Commit 4472beae 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-domain limited resource.
    
    Fix by marking the ioreq as mapped before calling ioreq_unmap in this
    situation.
    
    Signed-off-by: Matthew Daley <mattjd@xxxxxxxxx>
    Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
---
 hw/block/xen_disk.c |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
index 727f433..03e30d7 100644
--- a/hw/block/xen_disk.c
+++ b/hw/block/xen_disk.c
@@ -405,6 +405,7 @@ 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;
             }
--
generated by git-patchbot for /home/xen/git/qemu-upstream-unstable.git

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