virter vm ls segmentation fault when other non-virter libvirt VMs exist

[mmguero]

Not sure exactly when this started happening, but:

$ virter vm ls
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x1 addr=0x0 pc=0xa5ac5c]

goroutine 1 [running]:
github.com/LINBIT/virter/internal/virter.(*Virter).VMInfo(0xc000312180, {0xc0003262d0, 0x24})
    /home/user/devel/github/virter/internal/virter/vm.go:110 +0x29c
github.com/LINBIT/virter/cmd.vmCommand.vmListCommand.func1(0xc0002ba100?, {0x12e69a0?, 0x4?, 0xc94ed8?})
    /home/user/devel/github/virter/cmd/vm_list.go:35 +0x17a
github.com/spf13/cobra.(*Command).execute(0xc0002a8f08, {0x12e69a0, 0x0, 0x0})
    /home/user/.asdf/installs/golang/1.23.3/packages/pkg/mod/github.com/spf13/[email protected]/command.go:989 +0xa91
github.com/spf13/cobra.(*Command).ExecuteC(0xc000292308)
    /home/user/.asdf/installs/golang/1.23.3/packages/pkg/mod/github.com/spf13/[email protected]/command.go:1117 +0x3ff
github.com/spf13/cobra.(*Command).Execute(...)
    /home/user/.asdf/installs/golang/1.23.3/packages/pkg/mod/github.com/spf13/[email protected]/command.go:1041
github.com/spf13/cobra.(*Command).ExecuteContext(...)
    /home/user/.asdf/installs/golang/1.23.3/packages/pkg/mod/github.com/spf13/[email protected]/command.go:1034
github.com/LINBIT/virter/cmd.Execute()
    /home/user/devel/github/virter/cmd/root.go:86 +0x1ca
main.main()
    /home/user/devel/github/virter/main.go:8 +0xf

I was running v0.28.0 then checked out the latest revision and built from there (e36b0ba) but am getting the same issue.

$ apt-cache policy libvirt0:amd64
libvirt0:
  Installed: 9.0.0-4+deb12u2
  Candidate: 9.0.0-4+deb12u2
  Version table:
 *** 9.0.0-4+deb12u2 500
        500 http://ftp.debian.org/debian bookworm/main amd64 Packages
        100 /var/lib/dpkg/status

[mmguero]

If this helps:

I have some other vagrant-libvirt machines (not started by virter) on this machine:

id       name                         provider state   directory                                                               
-------------------------------------------------------------------------------------------------------------------------------
db905b0  vagrant-hedgehog-raspi-build libvirt shutoff /home/user/devel/github/Malcolm/hedgehog-raspi/vagrant 

in GDB at the point of the crash:

info local
&desc = 0xc0001d8400
&meta = 0xc000406960
dom = {
  Name = "vagrant_vagrant-hedgehog-raspi-build",
  UUID = "$$\234S \303LN\221\355\327!\"\263N\214",
  ID = -1
}
err = {
  tab = 0x0,
  data = 0x0
}
network = 0xc000184008
vmMac = {
  array = 0x120 <error: Cannot access memory at address 0x120>,
  len = 824635409536,
  cap = 6
}
xmldesc = "<domain type='kvm'>\n  <name>vagrant_vagrant-hedgehog-raspi-build ...

It looks like it's trying to list some information about this other non-virter libvirt VM, and vmMac is uninitialized?

[mmguero]

Also, for what it's worth, removing this other non-virter VM, the segfault does go away.

[JoelColledge]

The crash occurs on this line:

virter/internal/virter/vm.go

Line 110 in d834012

err = xml.Unmarshal([]byte(desc.Metadata.XML), &meta)

I'm guessing desc.Metadata is nil. We probably just need a

	if desc.Metadata == nil {
		// not a virter VM
		return &VMInfo{Name: vmName}, nil
	}

Preceding the meta unmarshaling. Does that work?

[mmguero]

Thanks, that does indeed solve the problem! I've opened #34 with that check.

[mmguero]

Thanks for merging! Not to be a hassle, but if it's convenient for you sometime to put out a release out containing the fix I'd appreciate it. And thanks again for looking at this.

[JoelColledge]

Released: https://github.com/LINBIT/virter/releases/tag/v0.28.1 ✅