util: require command args to be non-NULL

The virCommand APIs do not expect to be given a NULL value for an arg
name or value. Such a mistake can lead to execution of the wrong
command, as the NULL may prematurely terminate the list of args.
Detect this and report suitable error messages.

This identified a flaw in the storage test which was passing a NULL
instead of the volume path. This flaw was then validated by an incorrect
set of qemu-img args as expected data.

Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>

src/util/vircommand.c

@@ -1498,6 +1498,12 @@ virCommandAddArg(virCommandPtr cmd, const char *val)
     if (!cmd || cmd->has_error)
         return;
 
+    if (val == NULL) {
+        cmd->has_error = EINVAL;
+        abort();
+        return;
+    }
+
     if (VIR_STRDUP_QUIET(arg, val) < 0) {
         cmd->has_error = ENOMEM;
         return;
@@ -1595,6 +1601,10 @@ virCommandAddArgFormat(virCommandPtr cmd, const char *format, ...)
 void
 virCommandAddArgPair(virCommandPtr cmd, const char *name, const char *val)
 {
+    if (name == NULL || val == NULL) {
+        cmd->has_error = EINVAL;
+        return;
+    }
     virCommandAddArgFormat(cmd, "%s=%s", name, val);
 }
 

tests/storagevolxml2argvdata/qcow2-zerocapacity.argv

@@ -1 +1 @@
-qemu-img create -f qcow2 -o compat=0.10  0K
+qemu-img create -f qcow2 -o compat=0.10 /var/lib/libvirt/images/OtherDemo.img 0K

tests/storagevolxml2xmlin/vol-qcow2-zerocapacity.xml

@@ -1,6 +1,7 @@
 <volume>
   <name>OtherDemo.img</name>
   <target>
+    <path>/var/lib/libvirt/images/OtherDemo.img</path>
     <format type="qcow2"/>
   </target>
   <capacity>0</capacity>