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Bug 1588447

Summary:	Forbid relative paths for network disk unix socket
Product:	[Community] Virtualization Tools	Reporter:	Richard W.M. Jones <rjones>
Component:	libvirt	Assignee:	Libvirt Maintainers <libvirt-maint>
Status:	NEW ---	QA Contact:
Severity:	unspecified	Docs Contact:
Priority:	unspecified
Version:	unspecified	CC:	berrange, libvirt-maint, pkrempa
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Hardware:	Unspecified
OS:	Unspecified
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Clone Of:
Clones:	1588451 (view as bug list)		Environment:
Last Closed:		Type:	Bug
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oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
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Embargoed:
Bug Depends On:
Bug Blocks:	910269, 1588451

Description Richard W.M. Jones 2018-06-07 11:19:45 UTC

Description of problem:

https://www.redhat.com/archives/libvir-list/2018-June/msg00490.html

If you have a reference to a relative path for a socket,
these no longer work.  They used to in older versions of libvirt,
and they still work on certain architectures (for example, x86_64
still works, but i686 fails).

libvirt should either reject them if they are wrong, or be fixed
so that it works like it used to.

If you decide to reject them, please clone this bug for
libguestfs because we will need to fix the paths that we
pass to libvirt.

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

libvirt 4.4.0-1.fc29

How reproducible:

Unknown, only on certain architectures at certain times.
I was only able to reliably reproduce on i686 in a Koji
build using qemu:///session.

Steps to Reproduce:

1. Start nbdkit serving over a local Unix domain socket in the
current directory:

rm -f my.sock
nbdkit -f -v -U my.sock example1

2. Create a guest which has a disk like:

  <disk device="disk" type="network">
    <source protocol="nbd">
      <host transport="unix" socket="my.sock"/>
    </source>
    <target dev="sda" bus="scsi"/>
    <driver name="qemu" type="raw" cache="writeback"/>
  </disk>

3. Start the guest under qemu:///session

4. Fails with:

  internal error: process exited while connecting to monitor: 2018-06-06T17:02:5
4.450507Z qemu-system-i386: -drive
file=nbd+unix://?socket=my.sock,format=raw,if=none,id=drive-scsi0-0-0-0,cache=w
riteback: Failed to connect socket my.sock: No such file or directory [code=1
int1=-1]

Comment 1 Peter Krempa 2018-06-07 11:29:12 UTC

The XML schema for the network disk unix socket backing always called for an 'absFilePath' so the given XML is not valid.

I think we want to enforce absolute path even in the code for APPS which don't pass correct XML to libvirt.

Comment 2 Daniel Berrangé 2018-06-07 12:44:32 UTC

Even if we don't intend to support relative paths, I'm still left wondering what we changed in libvirt that breaks the way they used to work, especially because its said to be architecture specific breakage. I'm concerned that whatever the root cause was, may have an impact on something else that we do care about supporting