daemon: Fix crash in virTypedParameterArrayClear

CVE-2012-3445, https://bugzilla.redhat.com/show_bug.cgi?id=844745

Daemon uses the following pattern when dispatching APIs with typed
parameters:

    VIR_ALLOC_N(params, nparams);
    virDomain*(dom, params, &nparams, flags);
    virTypedParameterArrayClear(params, nparams);

In case nparams was originally set to 0, virDomain* API would fill it
with the number of typed parameters it can provide and we would use this
number (rather than zero) to clear params. Because VIR_ALLOC* returns
non-NULL pointer even if size is 0, the code would end up walking
through random memory. If we were lucky enough and the memory contained
7 (VIR_TYPED_PARAM_STRING) at the right place, we would try to free a
random pointer and crash.

Let's make sure params stays NULL when nparams is 0.
(cherry picked from commit 6039a2cb)

daemon/remote.c

@@ -964,7 +964,7 @@ remoteDispatchDomainGetSchedulerParameters(virNetServerPtr server ATTRIBUTE_UNUS
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0)
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0)
         goto no_memory;
 
     if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
@@ -1019,7 +1019,7 @@ remoteDispatchDomainGetSchedulerParametersFlags(virNetServerPtr server ATTRIBUTE
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0)
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0)
         goto no_memory;
 
     if (!(dom = get_nonnull_domain(priv->conn, args->dom)))
@@ -1200,7 +1200,7 @@ remoteDispatchDomainBlockStatsFlags(virNetServerPtr server ATTRIBUTE_UNUSED,
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }
@@ -1674,7 +1674,7 @@ remoteDispatchDomainGetMemoryParameters(virNetServerPtr server ATTRIBUTE_UNUSED,
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }
@@ -1739,7 +1739,7 @@ remoteDispatchDomainGetNumaParameters(virNetServerPtr server ATTRIBUTE_UNUSED,
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }
@@ -1804,7 +1804,7 @@ remoteDispatchDomainGetBlkioParameters(virNetServerPtr server ATTRIBUTE_UNUSED,
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }
@@ -2064,7 +2064,7 @@ remoteDispatchDomainGetBlockIoTune(virNetServerPtr server ATTRIBUTE_UNUSED,
         goto cleanup;
     }
 
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }
@@ -3563,7 +3563,7 @@ remoteDispatchDomainGetInterfaceParameters(virNetServerPtr server ATTRIBUTE_UNUS
         virNetError(VIR_ERR_INTERNAL_ERROR, "%s", _("nparams too large"));
         goto cleanup;
     }
-    if (VIR_ALLOC_N(params, nparams) < 0) {
+    if (nparams && VIR_ALLOC_N(params, nparams) < 0) {
         virReportOOMError();
         goto cleanup;
     }