Bug 811228

Summary: block streaming reverts image to auto-probe backing file format
Product: Red Hat Enterprise Linux 6 Reporter: Paolo Bonzini <pbonzini>
Component: qemu-kvmAssignee: Paolo Bonzini <pbonzini>
Status: CLOSED ERRATA QA Contact: Virtualization Bugs <virt-bugs>
Severity: unspecified Docs Contact:
Priority: unspecified    
Version: 6.3CC: acathrow, areis, bsarathy, dyasny, flang, juzhang, michen, minovotn, mkenneth, shu, virt-maint
Target Milestone: rc   
Target Release: ---   
Hardware: Unspecified   
OS: Unspecified   
Whiteboard:
Fixed In Version: qemu-kvm-0.12.1.2-2.278.el6 Doc Type: Bug Fix
Doc Text:
No Documentation Needed
Story Points: ---
Clone Of: Environment:
Last Closed: 2012-06-20 08:56:41 UTC Type: Bug
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:

Description Paolo Bonzini 2012-04-10 13:34:50 UTC
When an image is modified to point to the new backing file, the backing file format is set to NULL, which means auto-probe.  This is wrong, in fact it is a small security problem.

Comment 1 Paolo Bonzini 2012-04-10 13:43:31 UTC
How to test:

(qemu) snapshot_blkdev ide0-hd0 test.qcow2 qcow2
(qemu) snapshot_blkdev ide0-hd0 fff.qcow2 qcow2
(qemu) block_stream ide0-hd0 base.qcow2

On fixed QEMU, the fff.qcow2 will show something like ^Eqcow2^@^@^@base.qcow2 when viewed with less.

On broken QEMU, it will show something like base.qcow2ow2^@^@^@test.qcow2.

Comment 7 juzhang 2012-05-02 06:01:25 UTC
Verified this issue with qemu-kvm-rhev-0.12.1.2-2.288.el6

steps

1. boot guest with /root/zhang/rhel6.3-64-virtio.qcow2
2. snapshot_blkdev virtio0 /root/zhang/test1 qcow2
3. snapshot_blkdev virtio0 /root/zhang/test2 qcow2
4. block-stream virtio0   /root/zhang/rhel6.3-64-virtio.qcow2
5. view /root/test2 | less

Results
Eqcow2^@^@^@/root/zhang/rhel6.3-64-virtio.qcow2

Comment 9 Michal Novotny 2012-05-04 13:19:34 UTC
    Technical note added. If any revisions are required, please edit the "Technical Notes" field
    accordingly. All revisions will be proofread by the Engineering Content Services team.
    
    New Contents:
No Documentation Needed

Comment 11 errata-xmlrpc 2012-06-20 08:56:41 UTC
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

http://rhn.redhat.com/errata/RHBA-2012-1017.html