conf: Fix check for chardev source path

Attempting to use a chardev definition like

  <serial type='unix'>
    <target type='isa-serial'/>
  </serial>

correctly results in an error being reported, since the source
path - a required piece of information - is missing; however,
the very similar

  <serial type='unix'>
    <target type='pci-serial'/>
  </serial>

was happily accepted by libvirt, only to result in libvirtd
crashing as soon as the guest was started.

The issue was caused by checking the chardev's targetType
against whitelisted values from virDomainChrChannelTargetType
without first checking the chardev's deviceType to make sure
it is actually a channel, for which the check makes sense,
rather than a different type of chardev.

The only reason this wasn't spotted earlier is that the
whitelisted values just so happen to correspond to USB and
PCI serial devices and Xen and UML consoles respectively,
all of which are fairly uncommon.

https://bugzilla.redhat.com/show_bug.cgi?id=1609720Signed-off-by: NAndrea Bolognani <abologna@redhat.com>
Reviewed-by: NJán Tomko <jtomko@redhat.com>

src/conf/domain_conf.c

@@ -5467,11 +5467,14 @@ virDomainChrSourceDefValidate(const virDomainChrSourceDef *def,
         break;
 
     case VIR_DOMAIN_CHR_TYPE_UNIX:
-        /* path can be auto generated */
+        /* The source path can be auto generated for certain specific
+         * types of channels, but in most cases we should report an
+         * error if the user didn't provide it */
         if (!def->data.nix.path &&
-            (!chr_def ||
-             (chr_def->targetType != VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_XEN &&
-              chr_def->targetType != VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_VIRTIO))) {
+            !(chr_def &&
+              chr_def->deviceType == VIR_DOMAIN_CHR_DEVICE_TYPE_CHANNEL &&
+              (chr_def->targetType == VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_XEN ||
+               chr_def->targetType == VIR_DOMAIN_CHR_CHANNEL_TARGET_TYPE_VIRTIO))) {
             virReportError(VIR_ERR_INTERNAL_ERROR, "%s",
                            _("Missing source path attribute for char device"));
             return -1;

tests/qemuxml2argvdata/serial-unix-missing-source.xml

+<domain type='qemu'>
+  <name>guest</name>
+  <uuid>c7a5fdbd-edaf-9455-926a-d65c16db1809</uuid>
+  <memory unit='KiB'>1048576</memory>
+  <vcpu placement='static'>1</vcpu>
+  <os>
+    <type arch='aarch64' machine='virt'>hvm</type>
+  </os>
+  <devices>
+    <emulator>/usr/bin/qemu-system-aarch64</emulator>
+    <serial type='unix'>
+      <target type='pci-serial'/>
+    </serial>
+  </devices>
+</domain>

tests/qemuxml2argvtest.c

@@ -1417,6 +1417,7 @@ mymain(void)
     DO_TEST("serial-unix-chardev",
             QEMU_CAPS_DEVICE_ISA_SERIAL);
     DO_TEST_CAPS_LATEST("serial-unix-chardev");
+    DO_TEST_PARSE_ERROR("serial-unix-missing-source", NONE);
     DO_TEST("serial-tcp-chardev",
             QEMU_CAPS_DEVICE_ISA_SERIAL);
     DO_TEST("serial-udp-chardev",