Bug 581045

Summary:	'download' command corrupts very large files
Product:	[Community] Virtualization Tools	Reporter:	Richard W.M. Jones <rjones>
Component:	libguestfs	Assignee:	Richard W.M. Jones <rjones>
Status:	CLOSED NOTABUG	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	mbooth, virt-maint
Target Milestone:	---
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2010-05-15 16:30:11 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Richard W.M. Jones 2010-04-09 21:38:41 UTC

Description of problem:

Not entirely sure about this one, but I thought I observed a download
of a very large device producing a corrupt local file.

Version-Release number of selected component (if applicable):

1.3.1

How reproducible:

?

Steps to Reproduce:

Get md5 of some large (> 4 GB) device within an image :-

  guestfish --ro -a disk.img run : mkmountpoint /foo : checksum md5 /../dev/vda1

Download same device and checksum it :-

  guestfish --ro -a disk.img run : download /dev/vda1 local.img
  md5sum local.img

Actual results:

Difference found in a 10 GB image near to the 4 GB point.

Expected results:

Obviously there should be no difference.

Additional info:

Comment 1 Richard W.M. Jones 2010-05-12 15:35:07 UTC

Since we fixed another bug you can no longer use /.. to escape
from the appliance, so the reproducer from comment 0 no longer
works.

Instead do this with guestfish >= 1.3:

$ virt-list-partitions -hl /path/to/disk.img
/dev/sda1 ntfs 100.0M
/dev/sda2 ntfs 15.9G

Choose a large (> 4 GB) partition or LV, and then do:

$ guestfish --ro -a /path/to/disk.img run : checksum-device md5 /dev/sda2
7585d6e5fd2f7608ded54106dac0cc59

Then repeatedly download and checksum:

$ guestfish --ro -a /path/to/disk,img run : download /dev/sda2 local.img
$ md5sum local.img

repeating these last two commands until the checksum does not
match the first checksum.

Comment 2 Richard W.M. Jones 2010-05-15 12:48:33 UTC

I ran some very long tests on my machine, comparing the known
good disk image with subsequent downloads that were failing.

Comparative results are below (output from 'cmp -l' command -
the first number is the offset and the second and third numbers
are the good and bad bytes at this offset, in octal):

[image 1]
 4484845765 215 205
11416690693 234 334

[image 2]
16850120709 207 307
16850120773  47 147

[image 3]
16142352581 230 220

Based on this, I believe this is more likely to be a bit error
in the memory of my test machine.

I am continuing to perform the tests on other machines.

Comment 3 Richard W.M. Jones 2010-05-15 16:30:11 UTC

I cannot reproduce this on any other machine apart
from my first test machine.  Damn, memory error :-(
For now I am closing this as NOTABUG, please feel
free to reopen if it is ever reproduced.