commit 4cd3f241399eb691a7fc9a1279938bfe76215a77
Author: Wim ten Have <wim.ten.have@oracle.com>
Date:   Fri May 19 16:38:43 2017 +0200

    xenconfig: fix handling of NULL disk source
    
    It is possible to crash libvirtd when converting xl native config to
    domXML when the xl config contains an empty disk source, e.g. an empty
    CDROM. Fix by checking that the disk source is non-NULL before parsing it.
    
    Signed-off-by: Wim ten Have <wim.ten.have@oracle.com>

Index: libvirt-3.3.0/src/xenconfig/xen_xl.c
===================================================================
--- libvirt-3.3.0.orig/src/xenconfig/xen_xl.c
+++ libvirt-3.3.0/src/xenconfig/xen_xl.c
@@ -316,6 +316,10 @@ xenParseXLDiskSrc(virDomainDiskDefPtr di
     char *tmpstr = NULL;
     int ret = -1;
 
+    /* A NULL source is valid, e.g. an empty CDROM */
+    if (srcstr == NULL)
+        return 0;
+
     if (STRPREFIX(srcstr, "rbd:")) {
         if (!(tmpstr = virStringReplace(srcstr, "\\\\", "\\")))
             goto cleanup;
Index: libvirt-3.3.0/tests/xlconfigdata/test-disk-positional-parms-partial.cfg
===================================================================
--- libvirt-3.3.0.orig/tests/xlconfigdata/test-disk-positional-parms-partial.cfg
+++ libvirt-3.3.0/tests/xlconfigdata/test-disk-positional-parms-partial.cfg
@@ -22,4 +22,4 @@ parallel = "none"
 serial = "none"
 builder = "hvm"
 boot = "d"
-disk = [ "/dev/HostVG/XenGuest2,,hda,,backendtype=phy", "/var/lib/libvirt/images/XenGuest2-home,,hdb,,", "/root/boot.iso,,hdc,,devtype=cdrom" ]
+disk = [ "/dev/HostVG/XenGuest2,,hda,,backendtype=phy", "/var/lib/libvirt/images/XenGuest2-home,,hdb,,", "/root/boot.iso,,hdc,,devtype=cdrom" , "format=raw,vdev=hdd,access=ro,devtype=cdrom" ]
Index: libvirt-3.3.0/tests/xlconfigdata/test-disk-positional-parms-partial.xml
===================================================================
--- libvirt-3.3.0.orig/tests/xlconfigdata/test-disk-positional-parms-partial.xml
+++ libvirt-3.3.0/tests/xlconfigdata/test-disk-positional-parms-partial.xml
@@ -39,6 +39,12 @@
       <readonly/>
       <address type='drive' controller='0' bus='1' target='0' unit='0'/>
     </disk>
+    <disk type='file' device='cdrom'>
+      <driver name='qemu' type='raw'/>
+      <target dev='hdd' bus='ide'/>
+      <readonly/>
+      <address type='drive' controller='0' bus='1' target='0' unit='1'/>
+    </disk>
     <controller type='ide' index='0'/>
     <interface type='bridge'>
       <mac address='00:16:3e:66:92:9c'/>