dbcheck: don't remove dangling one-way links on already deleted objects

This would typically happen when the garbage collection
removed a parent object before a child object (both with
the DISALLOW_MOVE_ON_DELETE bit set in systemFlags),
while dbcheck is running at the same time as the garbage collection.
In this case the lastKnownParent attributes points a non existing
object.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=13816

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

1 files changed, 13 insertions, 0 deletions

diff --git a/python/samba/dbchecker.py b/python/samba/dbchecker.py
index f9a11af9df1..35cff3668f2 100644
--- a/python/samba/dbchecker.py
+++ b/python/samba/dbchecker.py
@@ -571,6 +571,19 @@ newSuperior: %s""" % (str(from_dn), str(to_rdn), str(to_base)))
     def err_missing_target_dn_or_GUID(self, dn, attrname, val, dsdb_dn):
         """handle a missing target DN (if specified, GUID form can't be found,
         and otherwise DN string form can't be found)"""
+
+        # Don't change anything if the object itself is deleted
+        if str(dn).find('\\0ADEL') != -1:
+            # We don't bump the error count as Samba produces these
+            # in normal operation
+            self.report("WARNING: no target object found for GUID "
+                        "component link %s in deleted object "
+                        "%s - %s" % (attrname, dn, val))
+            self.report("Not removing dangling one-way "
+                        "link on deleted object "
+                        "(tombstone garbage collection in progress?)")
+            return 0
+
         # check if its a backlink
         linkID, _ = self.get_attr_linkID_and_reverse_name(attrname)
         if (linkID & 1 == 0) and str(dsdb_dn).find('\\0ADEL') == -1: