[Qemu-devel] [PATCH 29/55] qcow2: Fix unaligned preallocated truncation

[Michael Roth <mdroth@linux.vnet.ibm.com>]

From: Max Reitz <mreitz@redhat.com>

A qcow2 image file's length is not required to have a length that is a
multiple of the cluster size.  However, qcow2_refcount_area() expects an
aligned value for its @start_offset parameter, so we need to round
@old_file_size up to the next cluster boundary.

Reported-by: Ping Li <pingl@redhat.com>
Bug: https://bugzilla.redhat.com/show_bug.cgi?id=1414049
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20171009215533.12530-2-mreitz@redhat.com
Cc: qemu-stable@nongnu.org
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
(cherry picked from commit e400ad1e1f0127b4fdabcb1c8de1e99be91788df)
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
---
 block/qcow2.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/block/qcow2.c b/block/qcow2.c
index a756bf9541..10e38074ad 100644
--- a/block/qcow2.c
+++ b/block/qcow2.c
@@ -3161,6 +3161,7 @@ static int qcow2_truncate(BlockDriverState *bs, int64_t offset,
                              "Failed to inquire current file length");
             return ret;
         }
+        old_file_size = ROUND_UP(old_file_size, s->cluster_size);
 
         nb_new_data_clusters = DIV_ROUND_UP(offset - old_length,
                                             s->cluster_size);
-- 
2.11.0