qemu: Tolerate storage source private data being NULL

In some cases it does not make sense to pursue that the private data
will be allocated (especially when we don't need to put anything in it).

Ensure that the code works without it.

This also fixes few crashes pointed out in
https://bugzilla.redhat.com/show_bug.cgi?id=1510323

src/qemu/qemu_command.c

@@ -1501,12 +1501,17 @@ qemuBuildDriveSourceStr(virDomainDiskDefPtr disk,
 {
     int actualType = virStorageSourceGetActualType(disk->src);
     qemuDomainStorageSourcePrivatePtr srcpriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
-    qemuDomainSecretInfoPtr secinfo = srcpriv->secinfo;
-    qemuDomainSecretInfoPtr encinfo = srcpriv->encinfo;
+    qemuDomainSecretInfoPtr secinfo = NULL;
+    qemuDomainSecretInfoPtr encinfo = NULL;
     virJSONValuePtr srcprops = NULL;
     char *source = NULL;
     int ret = -1;
 
+    if (srcpriv) {
+        secinfo = srcpriv->secinfo;
+        encinfo = srcpriv->encinfo;
+    }
+
     if (qemuDiskSourceNeedsProps(disk->src) &&
         !(srcprops = qemuDiskSourceGetProps(disk->src)))
         goto cleanup;
@@ -2191,8 +2196,13 @@ qemuBuildDiskDriveCommandLine(virCommandPtr cmd,
         bool driveBoot = false;
         virDomainDiskDefPtr disk = def->disks[i];
         qemuDomainStorageSourcePrivatePtr srcPriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
-        qemuDomainSecretInfoPtr secinfo = srcPriv->secinfo;
-        qemuDomainSecretInfoPtr encinfo = srcPriv->encinfo;
+        qemuDomainSecretInfoPtr secinfo = NULL;
+        qemuDomainSecretInfoPtr encinfo = NULL;
+
+        if (srcPriv) {
+            secinfo = srcPriv->secinfo;
+            encinfo = srcPriv->encinfo;
+        }
 
         if (disk->info.bootIndex) {
             bootindex = disk->info.bootIndex;

src/qemu/qemu_hotplug.c

@@ -259,6 +259,7 @@ qemuDomainChangeEjectableMedia(virQEMUDriverPtr driver,
     qemuDomainObjPrivatePtr priv = vm->privateData;
     qemuDomainDiskPrivatePtr diskPriv = QEMU_DOMAIN_DISK_PRIVATE(disk);
     qemuDomainStorageSourcePrivatePtr srcPriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
+    qemuDomainSecretInfoPtr secinfo = NULL;
     const char *format = NULL;
     char *sourcestr = NULL;
 
@@ -268,6 +269,9 @@ qemuDomainChangeEjectableMedia(virQEMUDriverPtr driver,
         goto cleanup;
     }
 
+    if (srcPriv)
+        secinfo = srcPriv->secinfo;
+
     if (disk->device != VIR_DOMAIN_DISK_DEVICE_FLOPPY &&
         disk->device != VIR_DOMAIN_DISK_DEVICE_CDROM) {
         virReportError(VIR_ERR_INTERNAL_ERROR,
@@ -300,7 +304,7 @@ qemuDomainChangeEjectableMedia(virQEMUDriverPtr driver,
     }
 
     if (!virStorageSourceIsEmpty(newsrc)) {
-        if (qemuGetDriveSourceString(newsrc, srcPriv->secinfo, &sourcestr) < 0)
+        if (qemuGetDriveSourceString(newsrc, secinfo, &sourcestr) < 0)
             goto error;
 
         if (virStorageSourceGetActualType(newsrc) != VIR_STORAGE_TYPE_DIR) {
@@ -371,8 +375,8 @@ qemuDomainAttachDiskGeneric(virConnectPtr conn,
     virJSONValuePtr secobjProps = NULL;
     virJSONValuePtr encobjProps = NULL;
     qemuDomainStorageSourcePrivatePtr srcPriv;
-    qemuDomainSecretInfoPtr secinfo;
-    qemuDomainSecretInfoPtr encinfo;
+    qemuDomainSecretInfoPtr secinfo = NULL;
+    qemuDomainSecretInfoPtr encinfo = NULL;
 
     if (qemuDomainPrepareDisk(driver, vm, disk, NULL, false) < 0)
         goto cleanup;
@@ -384,13 +388,16 @@ qemuDomainAttachDiskGeneric(virConnectPtr conn,
         goto error;
 
     srcPriv = QEMU_DOMAIN_STORAGE_SOURCE_PRIVATE(disk->src);
-    secinfo = srcPriv->secinfo;
+    if (srcPriv) {
+        secinfo = srcPriv->secinfo;
+        encinfo = srcPriv->encinfo;
+    }
+
     if (secinfo && secinfo->type == VIR_DOMAIN_SECRET_INFO_TYPE_AES) {
         if (qemuBuildSecretInfoProps(secinfo, &secobjProps) < 0)
             goto error;
     }
 
-    encinfo = srcPriv->encinfo;
     if (encinfo && qemuBuildSecretInfoProps(encinfo, &encobjProps) < 0)
         goto error;