From 1cde230fc97b87b37e8fe78028d07c2c58143bdd Mon Sep 17 00:00:00 2001
From: Mark Reynolds <mreynolds@redhat.com>
Date: Jul 20 2015 20:35:09 +0000
Subject: Ticket 48206 - Crash during retro changelog trimming


Bug Description:  If the retro changelog entry is small, its possible that
                  during the trimming the reto changelog entry is not in the
                  cache after the trim, but its tries to blindly unlock it
                  from the cache, which leads to a crash.

FIx Description:  After we call the post op plugins and retrieve the entry
                  from the cache, double check that it was found.  If it
                  is not found, do not unlock it.

https://fedorahosted.org/389/ticket/48206

Reviewed by: nhosoi(Thanks!)

(cherry picked from commit 2a8a8c8ced5849dada34ab28d79e87dd3636e413)

---

diff --git a/ldap/servers/slapd/back-ldbm/ldbm_delete.c b/ldap/servers/slapd/back-ldbm/ldbm_delete.c
index 619ff4a..4f97c2b 100644
--- a/ldap/servers/slapd/back-ldbm/ldbm_delete.c
+++ b/ldap/servers/slapd/back-ldbm/ldbm_delete.c
@@ -1286,17 +1286,24 @@ ldbm_back_delete( Slapi_PBlock *pb )
 				CACHE_RETURN(&inst->inst_cache, &e);
 			}
 		}
-		if (cache_is_in_cache(&inst->inst_cache, e)) {
-			ep_id = e->ep_id; /* Otherwise, e might have been freed. */
-			CACHE_REMOVE(&inst->inst_cache, e);
-		}
-		cache_unlock_entry(&inst->inst_cache, e);
-		CACHE_RETURN(&inst->inst_cache, &e);
-		/* 
-		 * e is unlocked and no longer in cache.
-		 * It could be freed at any moment.
+
+		/*
+		 * e could have been replaced by cache_find_id(), recheck if it's NULL
+		 * before trying to unlock it, etc.
 		 */
-		e = NULL;
+		if (e) {
+			if (cache_is_in_cache(&inst->inst_cache, e)) {
+				ep_id = e->ep_id; /* Otherwise, e might have been freed. */
+				CACHE_REMOVE(&inst->inst_cache, e);
+			}
+			cache_unlock_entry(&inst->inst_cache, e);
+			CACHE_RETURN(&inst->inst_cache, &e);
+			/*
+			 * e is unlocked and no longer in cache.
+			 * It could be freed at any moment.
+			 */
+			e = NULL;
+		}
 
 		if (entryrdn_get_switch() && ep_id) { /* subtree-rename: on */
 			/* since the op was successful, delete the tombstone dn from the dn cache */