On Fri, Jun 01, 2018 at 07:59:51AM +0300, Mykola Ivanets wrote:

I saw several Windows disk images which contains strange registry entry for mapped drives:

"\\DosDevices\\Y:"=hex(3):00,00,00,00,00,00,00,00,00,00,00,00

Which is decoded something like diskID = 0x0, partition starts at 0 bytes offset from the start of the disk. In addition to a Windows disk image, I have attached dummy disk and made xfs file system on a whole device without partitioning it. I mount xfs file system to a "/" and then mkdir and mount other found file systems inside (/fs1, /fs2 etc.).

When we decode drive mappings we are looking for a disk with ID 0x0 (it is 4 bytes somewhere LBA0). It is appeared that dummy non-partitioned disk with xfs file system has zeros by offset where diskID is expected to be). So the disk is considered as a candidate to search for partition at offset 0. part-list command (and "parted" which is used under the hood) reports there is 1 partition on "dummy" disk which starts exactly at offset 0. And thus dummy device name and partition number are simply concatenated together and corresponding drive mapping is returned: Y => /dev/sdX1. But /dev/sdX1 is not existing block device.

No matter either it is a bug in "parted" (or it works this way by-design), let's protect ourself from this situation: in addition we look for msdos partition table on a disk before making any further assumptions. --- daemon/inspect_fs_windows.ml | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/daemon/inspect_fs_windows.ml b/daemon/inspect_fs_windows.ml index 8b2aad8d3..af52dee2d 100644 --- a/daemon/inspect_fs_windows.ml +++ b/daemon/inspect_fs_windows.ml @@ -329,7 +329,7 @@ and get_drive_mappings h root data = String.is_prefix blob "DMIO:ID:" (* GPT *) then map_registry_disk_blob_gpt (Lazy.force partitions) blob else if String.length blob = 12 then - map_registry_disk_blob (Lazy.force devices) blob + map_registry_disk_blob_mbr (Lazy.force devices) blob else None ) @@ -356,13 +356,18 @@ and get_drive_mappings h root data = * The following function maps this blob to a libguestfs partition * name, if possible. *) -and map_registry_disk_blob devices blob = +and map_registry_disk_blob_mbr devices blob = try (* First 4 bytes are the disk ID. Search all devices to find the * disk with this disk ID. *) let diskid = String.sub blob 0 4 in - let device = List.find (fun dev -> pread dev 4 0x01b8 = diskid) devices in + let device = + List.find ( + fun dev -> + Parted.part_get_parttype dev = "msdos" && + pread dev 4 0x01b8 = diskid + ) devices in

Looks sensible, ACK. Will push it in a bit, thanks. Rich. -- Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones Read my programming and virtualization blog: http://rwmj.wordpress.com virt-builder quickly builds VMs from scratch http://libguestfs.org/virt-builder.1.html