xen-blkback: don't leak persistent grants from xen_blkbk_map()

The fix for XSA-365 zapped too many of the ->persistent_gnt[] entries.
Ones successfully obtained should not be overwritten, but instead left
for xen_blkbk_unmap_prepare() to pick up and put.

This is XSA-371.

Signed-off-by: Jan Beulich <jbeulich@suse.com>
Cc: stable@vger.kernel.org
Reviewed-by: Juergen Gross <jgross@suse.com>
Reviewed-by: Wei Liu <wl@xen.org>
Signed-off-by: Juergen Gross <jgross@suse.com>

diff --git a/drivers/block/xen-blkback/blkback.c b/drivers/block/xen-blkback/blkback.c
index da16121140cab23b8840e2aaa72131c795df8099..3874233f7194d9a2c2a9774ea8281052198575b6 100644 (file)
--- a/drivers/block/xen-blkback/blkback.c
+++ b/drivers/block/xen-blkback/blkback.c
@@ -891,7 +891,7 @@ next:
 out:
        for (i = last_map; i < num; i++) {
                /* Don't zap current batch's valid persistent grants. */
-               if(i >= last_map + segs_to_map)
+               if(i >= map_until)
                        pages[i]->persistent_gnt = NULL;
                pages[i]->handle = BLKBACK_INVALID_HANDLE;
        }