virSecurityLabelDefParseXML: Don't parse label on model='none'

https://bugzilla.redhat.com/show_bug.cgi?id=1027096

If there's the following snippet in the domain XML, the domain will be
lost upon the daemon restart (if the domain is started prior restart):

    <seclabel type='dynamic' relabel='yes'/>

The problem is, the 'label', 'imagelabel' and 'baselabel' are parsed
whenever the VIR_DOMAIN_XML_INACTIVE is *not* present or the label is
static. The latter is not our case, obviously. So, when libvirtd starts
up, it finds domain state xml and parse it. During parsing, many XML
flags are enabled but VIR_DOMAIN_XML_INACTIVE. Hence, our parser tries
to extract 'label', 'imagelabel' and 'baselabel' from the XML which
fails for model='none'. Err, this model - even though not specified in
XML - can be taken from qemu wide config file: /etc/libvirtd/qemu.conf.

However, in order to know we are dealing with model='none' the code in
question must be moved forward a bit. Then a new check must be
introduced. This is what the first two chunks are doing.

But this alone is not sufficient. The domain state XML won't contain the
model attribute without slight modification. The model should be
inserted into the XML even if equal to 'none' and the state XML is being
generated - what if the origin (the @security_driver variable in
qemu.conf) changes during libvirtd restarts?

At the end, a test to catch this scenario is introduced.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

src/conf/domain_conf.c

@@ -4370,6 +4370,17 @@ virSecurityLabelDefParseXML(xmlXPathContextPtr ctxt,
             def->norelabel = false;
     }
 
+    /* Always parse model */
+    p = virXPathStringLimit("string(./@model)",
+                            VIR_SECURITY_MODEL_BUFLEN-1, ctxt);
+    def->model = p;
+
+    /* For the model 'none' none of the following labels is going to be
+     * present. Hence, return now. */
+
+    if (STREQ_NULLABLE(def->model, "none"))
+        return def;
+
     /* Only parse label, if using static labels, or
      * if the 'live' VM XML is requested
      */
@@ -4408,11 +4419,6 @@ virSecurityLabelDefParseXML(xmlXPathContextPtr ctxt,
         def->baselabel = p;
     }
 
-    /* Always parse model */
-    p = virXPathStringLimit("string(./@model)",
-                            VIR_SECURITY_MODEL_BUFLEN-1, ctxt);
-    def->model = p;
-
     return def;
 
 error:
@@ -14177,7 +14183,9 @@ virDomainEventActionDefFormat(virBufferPtr buf,
 
 
 static void
-virSecurityLabelDefFormat(virBufferPtr buf, virSecurityLabelDefPtr def)
+virSecurityLabelDefFormat(virBufferPtr buf,
+                          virSecurityLabelDefPtr def,
+                          unsigned flags)
 {
     const char *sectype = virDomainSeclabelTypeToString(def->type);
 
@@ -14196,7 +14204,9 @@ virSecurityLabelDefFormat(virBufferPtr buf, virSecurityLabelDefPtr def)
     virBufferAsprintf(buf, "<seclabel type='%s'",
                       sectype);
 
-    if (def->model && STRNEQ(def->model, "none"))
+    /* When generating state XML do include the model */
+    if (flags & VIR_DOMAIN_XML_INTERNAL_STATUS ||
+        STRNEQ_NULLABLE(def->model, "none"))
         virBufferEscapeString(buf, " model='%s'", def->model);
 
     if (def->type == VIR_DOMAIN_SECLABEL_NONE) {
@@ -17107,7 +17117,7 @@ virDomainDefFormatInternal(virDomainDefPtr def,
 
     virBufferAdjustIndent(buf, 2);
     for (n = 0; n < def->nseclabels; n++)
-        virSecurityLabelDefFormat(buf, def->seclabels[n]);
+        virSecurityLabelDefFormat(buf, def->seclabels[n], flags);
     virBufferAdjustIndent(buf, -2);
 
     if (def->namespaceData && def->ns.format) {

tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-relabel.args

@@ -0,0 +1,6 @@
+LC_ALL=C PATH=/bin HOME=/home/test USER=test LOGNAME=test QEMU_AUDIO_DRV=none \
+/usr/bin/qemu \
+-name QEMUGuest1 -S -M pc -m 214 -smp 1 -nographic -monitor \
+unix:/tmp/test-monitor,server,nowait -no-acpi -boot c -usb \
+-hda /dev/HostVG/QEMUGuest1 -net none -serial \
+none -parallel none

tests/qemuxml2argvdata/qemuxml2argv-seclabel-dynamic-relabel.xml

@@ -0,0 +1,28 @@
+<domain type='qemu'>
+  <name>QEMUGuest1</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>219100</memory>
+  <currentMemory unit='KiB'>219100</currentMemory>
+  <vcpu placement='static' cpuset='1-4,8-20,525'>1</vcpu>
+  <os>
+    <type arch='i686' machine='pc'>hvm</type>
+    <boot dev='hd'/>
+  </os>
+  <clock offset='utc'/>
+  <on_poweroff>destroy</on_poweroff>
+  <on_reboot>restart</on_reboot>
+  <on_crash>destroy</on_crash>
+  <devices>
+    <emulator>/usr/bin/qemu</emulator>
+    <disk type='block' device='disk'>
+      <source dev='/dev/HostVG/QEMUGuest1'/>
+      <target dev='hda' bus='ide'/>
+      <address type='drive' controller='0' bus='0' target='0' unit='0'/>
+    </disk>
+    <controller type='usb' index='0'/>
+    <controller type='ide' index='0'/>
+    <controller type='pci' index='0' model='pci-root'/>
+    <memballoon model='virtio'/>
+  </devices>
+  <seclabel type='dynamic' relabel='yes'/>
+</domain>

tests/qemuxml2argvtest.c

@@ -963,6 +963,7 @@ mymain(void)
     DO_TEST("seclabel-dynamic-baselabel", QEMU_CAPS_NAME);
     DO_TEST("seclabel-dynamic-override", QEMU_CAPS_NAME);
     DO_TEST("seclabel-dynamic-labelskip", QEMU_CAPS_NAME);
+    DO_TEST("seclabel-dynamic-relabel", QEMU_CAPS_NAME);
     DO_TEST("seclabel-static", QEMU_CAPS_NAME);
     DO_TEST("seclabel-static-relabel", QEMU_CAPS_NAME);
     DO_TEST("seclabel-static-labelskip", QEMU_CAPS_NAME);

tests/qemuxml2xmltest.c

@@ -263,6 +263,7 @@ mymain(void)
     DO_TEST_FULL("seclabel-dynamic-baselabel", false, WHEN_INACTIVE);
     DO_TEST_FULL("seclabel-dynamic-override", false, WHEN_INACTIVE);
     DO_TEST_FULL("seclabel-dynamic-labelskip", true, WHEN_INACTIVE);
+    DO_TEST_FULL("seclabel-dynamic-relabel", false, WHEN_INACTIVE);
     DO_TEST("seclabel-static");
     DO_TEST_FULL("seclabel-static-labelskip", false, WHEN_ACTIVE);
     DO_TEST("seclabel-none");