qcow2: Read outside array bounds in qcow2_pre_write_overlap_check()

qcow2: Read outside array bounds in qcow2_pre_write_overlap_check()

The commit for 0e4e4318eaa5 increments QCOW2_OL_MAX_BITNR but does not
add an array entry for QCOW2_OL_BITMAP_DIRECTORY_BITNR to metadata_ol_names[].
As a result, an array dereference of metadata_ol_names[8] in
qcow2_pre_write_overlap_check() could result in a read outside of the array bounds.

Fixes: 0e4e4318eaa5 ('qcow2: add overlap check for bitmap directory')
Cc: Vladimir Sementsov-Ogievskiy <[email protected]>
Signed-off-by: Liam Merwick <[email protected]>
Reviewed-by: Eric Blake <[email protected]>
Reviewed-by: Max Reitz <[email protected]>
Message-id: 1541453919[email protected]
Signed-off-by: Max Reitz <[email protected]>