Description of problem:
When the fs pool target has been mounted, the inactive fs pool always autostarts while libvirtd starts up. It does not check whether the source /proc/mounts matches the source device in fs pool xml. The pool starts up even though using null as the source device in fs pool config xml.

Version-Release number of selected component (if applicable):
libvirt-1.2.8-12.el7.x86_64

How reproducible:
100%

Steps to Reproduce:
1. Prepare an inactive fs pool
# virsh pool-list --all
 Name                 State      Autostart
-------------------------------------------
fs                   inactive   no

2. # virsh pool-dumpxml fs
<pool type='fs'>
  <name>fs</name>
  <uuid>93709095-8f44-45ad-a2c9-15fc5e2cd410</uuid>
  <capacity unit='bytes'>75125227520</capacity>
  <allocation unit='bytes'>58557726720</allocation>
  <available unit='bytes'>16567500800</available>
  <source>
    <device path='/dev/sdc'/>    OR   <device path=''/>----> here using null as device
    <format type='xfs'/>
  </source>
  <target>
    <path>/tmp/fs</path>
    <permissions>
      <mode>0755</mode>
      <owner>-1</owner>
      <group>-1</group>
    </permissions>
  </target>
</pool>

3. mount a nfs server to /tmp/fs
# mount $ip:/var/lib/libvirt/images/ /tmp/fs
#mount
$ip:/var/lib/libvirt/images on /tmp/fs type nfs4 (rw,relatime,vers=4.0,
rsize=1048576,wsize=1048576,namlen=255,hard,proto=tcp,port=0,timeo=600,
retrans=2,sec=sys,clientaddr=$ip,local_lock=none,addr=$ip)

4. restart libvirtd
# service libvirtd restart
Redirecting to /bin/systemctl restart  libvirtd.service

# virsh pool-list --all
Name                 State      Autostart
-------------------------------------------
fs                   active     no

Actual Results: 
the fs pool always starts up while libvirtd starts



Expected results:


Additional info:
Following info from Daniel, 
that sounds like libvirt needs todo strict validation before
marking the pool as active. I guess we only check whether the
target directory is present in /proc/mounts. We'll need to add
a check on the source in /proc/mounts too.