block/backup: fix backup_cow_with_offload for last cluster

We shouldn't try to copy bytes beyond EOF. Fix it.

Fixes: 9ded4a0114968e
Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Message-id: 20190920142056.12778-3-vsementsov@virtuozzo.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit 1048ddf0a32dcdaa952e581bd503d49adad527cc)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>

diff --git a/block/backup.c b/block/backup.c
index 7067d1d1ad2384a025e4ab3815a142bfec3c679d..8761f1f9a7faacdeb57af8b66c789516e2d36bc2 100644 (file)
--- a/block/backup.c
+++ b/block/backup.c
@@ -167,7 +167,7 @@ static int coroutine_fn backup_cow_with_offload(BackupBlockJob *job,
 
     assert(QEMU_IS_ALIGNED(job->copy_range_size, job->cluster_size));
     assert(QEMU_IS_ALIGNED(start, job->cluster_size));
-    nbytes = MIN(job->copy_range_size, end - start);
+    nbytes = MIN(job->copy_range_size, MIN(end, job->len) - start);
     nr_clusters = DIV_ROUND_UP(nbytes, job->cluster_size);
     hbitmap_reset(job->copy_bitmap, start, job->cluster_size * nr_clusters);
     ret = blk_co_copy_range(blk, start, job->target, start, nbytes,