libvirt-<module>: Check caller-provided buffers to be NULL with size > 0

Pre-Glib era which used malloc allowed the size of the client-side
buffers to be declared as 0, because malloc documents that it can either
return 0 or a unique pointer on 0 size allocations.
With glib this doesn't work anymore, because glib documents that for
such allocation requests NULL is always returned which results in an
error in our public API checks server-side.
This patch complements the fix in the RPC layer by explicitly erroring
out on the following combination of args used by our legacy APIs (their
moder equivalents don't suffer from this):

function(caller-allocated-array, size, ...) {
    if (!caller-allocated-array && size > 0)
        return error;
}

treating everything else as a valid input and potentially let that fail
on the server-side rather than client-side.

https://bugzilla.redhat.com/show_bug.cgi?id=1772842

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>

src/internal.h

@@ -429,6 +429,19 @@
         } \
     } while (0)
 
+/* This check is intended to be used with legacy APIs only which expect the
+ * caller to pre-allocate the target buffer.
+ * We want to allow callers pass NULL arrays if the size is declared as 0 and
+ * still succeed in calling the API.
+ */
+#define virCheckNonNullArrayArgGoto(argname, argsize, label) \
+    do { \
+        if (!argname && argsize > 0) { \
+            virReportInvalidNonNullArg(argname); \
+            goto label; \
+        } \
+    } while (0)
+
 
 /* Count leading zeros in an unsigned int.
  *

src/libvirt-domain-snapshot.c

@@ -398,7 +398,7 @@ virDomainSnapshotListNames(virDomainPtr domain, char **names, int nameslen,
     virCheckDomainReturn(domain, -1);
     conn = domain->conn;
 
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, nameslen, error);
     virCheckNonNegativeArgGoto(nameslen, error);
 
     if (conn->driver->domainSnapshotListNames) {
@@ -600,7 +600,7 @@ virDomainSnapshotListChildrenNames(virDomainSnapshotPtr snapshot,
     virCheckDomainSnapshotReturn(snapshot, -1);
     conn = snapshot->domain->conn;
 
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, nameslen, error);
     virCheckNonNegativeArgGoto(nameslen, error);
 
     if (conn->driver->domainSnapshotListChildrenNames) {

src/libvirt-domain.c

@@ -59,7 +59,7 @@ virConnectListDomains(virConnectPtr conn, int *ids, int maxids)
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(ids, error);
+    virCheckNonNullArrayArgGoto(ids, maxids, error);
     virCheckNonNegativeArgGoto(maxids, error);
 
     if (conn->driver->connectListDomains) {
@@ -6386,7 +6386,7 @@ virConnectListDefinedDomains(virConnectPtr conn, char **const names,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->driver->connectListDefinedDomains) {
@@ -7298,7 +7298,7 @@ virDomainGetVcpuPinInfo(virDomainPtr domain, int ncpumaps,
     virCheckDomainReturn(domain, -1);
     conn = domain->conn;
 
-    virCheckNonNullArgGoto(cpumaps, error);
+    virCheckNonNullArrayArgGoto(cpumaps, ncpumaps, error);
     virCheckPositiveArgGoto(ncpumaps, error);
     virCheckPositiveArgGoto(maplen, error);
 
@@ -10996,10 +10996,7 @@ virDomainGetDiskErrors(virDomainPtr dom,
 
     virCheckDomainReturn(dom, -1);
 
-    if (maxerrors)
-        virCheckNonNullArgGoto(errors, error);
-    else
-        virCheckNullArgGoto(errors, error);
+    virCheckNonNullArrayArgGoto(errors, maxerrors, error);
 
     if (dom->conn->driver->domainGetDiskErrors) {
         int ret = dom->conn->driver->domainGetDiskErrors(dom, errors,
@@ -11136,10 +11133,7 @@ virDomainFSFreeze(virDomainPtr dom,
 
     virCheckDomainReturn(dom, -1);
     virCheckReadOnlyGoto(dom->conn->flags, error);
-    if (nmountpoints)
-        virCheckNonNullArgGoto(mountpoints, error);
-    else
-        virCheckNullArgGoto(mountpoints, error);
+    virCheckNonNullArrayArgGoto(mountpoints, nmountpoints, error);
 
     if (dom->conn->driver->domainFSFreeze) {
         int ret = dom->conn->driver->domainFSFreeze(
@@ -11181,10 +11175,7 @@ virDomainFSThaw(virDomainPtr dom,
 
     virCheckDomainReturn(dom, -1);
     virCheckReadOnlyGoto(dom->conn->flags, error);
-    if (nmountpoints)
-        virCheckNonNullArgGoto(mountpoints, error);
-    else
-        virCheckNullArgGoto(mountpoints, error);
+    virCheckNonNullArrayArgGoto(mountpoints, nmountpoints, error);
 
     if (dom->conn->driver->domainFSThaw) {
         int ret = dom->conn->driver->domainFSThaw(

src/libvirt-host.c

@@ -910,7 +910,7 @@ virNodeGetCellsFreeMemory(virConnectPtr conn, unsigned long long *freeMems,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(freeMems, error);
+    virCheckNonNullArrayArgGoto(freeMems, maxCells, error);
     virCheckPositiveArgGoto(maxCells, error);
     virCheckNonNegativeArgGoto(startCell, error);
 

src/libvirt-interface.c

@@ -166,7 +166,7 @@ virConnectListInterfaces(virConnectPtr conn, char **const names, int maxnames)
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->interfaceDriver && conn->interfaceDriver->connectListInterfaces) {
@@ -245,7 +245,7 @@ virConnectListDefinedInterfaces(virConnectPtr conn,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->interfaceDriver && conn->interfaceDriver->connectListDefinedInterfaces) {

src/libvirt-network.c

@@ -175,7 +175,7 @@ virConnectListNetworks(virConnectPtr conn, char **const names, int maxnames)
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->networkDriver && conn->networkDriver->connectListNetworks) {
@@ -252,7 +252,7 @@ virConnectListDefinedNetworks(virConnectPtr conn, char **const names,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->networkDriver && conn->networkDriver->connectListDefinedNetworks) {

src/libvirt-nodedev.c

@@ -169,7 +169,7 @@ virNodeListDevices(virConnectPtr conn,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->nodeDeviceDriver && conn->nodeDeviceDriver->nodeListDevices) {
@@ -415,7 +415,7 @@ virNodeDeviceListCaps(virNodeDevicePtr dev,
     virResetLastError();
 
     virCheckNodeDeviceReturn(dev, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (dev->conn->nodeDeviceDriver && dev->conn->nodeDeviceDriver->nodeDeviceListCaps) {

src/libvirt-nwfilter.c

@@ -127,7 +127,7 @@ virConnectListNWFilters(virConnectPtr conn, char **const names, int maxnames)
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->nwfilterDriver && conn->nwfilterDriver->connectListNWFilters) {

src/libvirt-secret.c

@@ -166,7 +166,7 @@ virConnectListSecrets(virConnectPtr conn, char **uuids, int maxuuids)
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(uuids, error);
+    virCheckNonNullArrayArgGoto(uuids, maxuuids, error);
     virCheckNonNegativeArgGoto(maxuuids, error);
 
     if (conn->secretDriver != NULL && conn->secretDriver->connectListSecrets != NULL) {

src/libvirt-storage.c

@@ -197,7 +197,7 @@ virConnectListStoragePools(virConnectPtr conn,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->storageDriver && conn->storageDriver->connectListStoragePools) {
@@ -277,7 +277,7 @@ virConnectListDefinedStoragePools(virConnectPtr conn,
     virResetLastError();
 
     virCheckConnectReturn(conn, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (conn->storageDriver && conn->storageDriver->connectListDefinedStoragePools) {
@@ -1268,7 +1268,7 @@ virStoragePoolListVolumes(virStoragePoolPtr pool,
     virResetLastError();
 
     virCheckStoragePoolReturn(pool, -1);
-    virCheckNonNullArgGoto(names, error);
+    virCheckNonNullArrayArgGoto(names, maxnames, error);
     virCheckNonNegativeArgGoto(maxnames, error);
 
     if (pool->conn->storageDriver && pool->conn->storageDriver->storagePoolListVolumes) {