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From 2c56e7dc08a41fc1dfa6a79213e93686f553847c Mon Sep 17 00:00:00 2001
From: William Brown <firstyear@redhat.com>
Date: Mon, 11 Dec 2017 15:48:24 +0100
Subject: [PATCH] Ticket 49495 - Fix memory management is vattr.

Bug Description:  During the fix for
https://pagure.io/389-ds-base/issue/49436 a issue was exposed
in how registration of attributes to cos work. With the change
to handle -> attr link, this exposed that cos treats each attribute
and template pair as a new type for the handle. As  aresult, this
caused the sp_list to create a long linked list of M*N entries
for each attr - template value. Obviously, this is extremely
slow to traverse during a search!

Fix Description:  Undo part of the SLL next change and convert
to reference counting. The issue remains that there is a defect
in how cos handles attribute registration, but this can not be
resolved without a significant rearchitecture of the code
related to virtual attributes.

https://pagure.io/389-ds-base/issue/49495

Author: wibrown

Review by: tbordaz, lkrispen (Thanks!)
---
 ldap/servers/plugins/cos/cos_cache.c | 28 +++++++++++-----------------
 ldap/servers/slapd/vattr.c           | 23 +++++++++++++++++++++--
 2 files changed, 32 insertions(+), 19 deletions(-)

diff --git a/ldap/servers/plugins/cos/cos_cache.c b/ldap/servers/plugins/cos/cos_cache.c
index 662dace35..3b3c05783 100644
--- a/ldap/servers/plugins/cos/cos_cache.c
+++ b/ldap/servers/plugins/cos/cos_cache.c
@@ -275,7 +275,7 @@ static Slapi_Mutex *start_lock;
 static Slapi_Mutex *stop_lock;
 static Slapi_CondVar *something_changed = NULL;
 static Slapi_CondVar *start_cond = NULL;
-
+static vattr_sp_handle *vattr_handle = NULL;
 
 /*
     cos_cache_init
@@ -314,6 +314,15 @@ cos_cache_init(void)
         goto out;
     }
 
+    if (slapi_vattrspi_register((vattr_sp_handle **)&vattr_handle,
+                                cos_cache_vattr_get,
+                                cos_cache_vattr_compare,
+                                cos_cache_vattr_types) != 0) {
+        slapi_log_err(SLAPI_LOG_ERR, COS_PLUGIN_SUBSYSTEM, "cos_cache_init - Cannot register as service provider\n");
+        ret = -1;
+        goto out;
+    }
+
     /* grab the views interface */
     if (slapi_apib_get_interface(Views_v1_0_GUID, &views_api)) {
         /* lets be tolerant if views is disabled */
@@ -847,22 +856,7 @@ cos_dn_defs_cb(Slapi_Entry *e, void *callback_data)
                                           dnVals[valIndex]->bv_val);
                 }
 
-                /*
-                 * Each SP_handle is associated to one and only one vattr.
-                 * We could consider making this a single function rather
-                 * than the double-call.
-                 */
-
-                vattr_sp_handle *vattr_handle = NULL;
-
-                if (slapi_vattrspi_register((vattr_sp_handle **)&vattr_handle,
-                                            cos_cache_vattr_get,
-                                            cos_cache_vattr_compare,
-                                            cos_cache_vattr_types) != 0) {
-                    slapi_log_err(SLAPI_LOG_ERR, COS_PLUGIN_SUBSYSTEM, "cos_cache_init - Cannot register as service provider for %s\n", dnVals[valIndex]->bv_val);
-                } else {
-                    slapi_vattrspi_regattr((vattr_sp_handle *)vattr_handle, dnVals[valIndex]->bv_val, NULL, NULL);
-                }
+                slapi_vattrspi_regattr((vattr_sp_handle *)vattr_handle, dnVals[valIndex]->bv_val, NULL, NULL);
 
             } /* if(attrType is cosAttribute) */
 
diff --git a/ldap/servers/slapd/vattr.c b/ldap/servers/slapd/vattr.c
index 432946c79..13e527188 100644
--- a/ldap/servers/slapd/vattr.c
+++ b/ldap/servers/slapd/vattr.c
@@ -1544,6 +1544,7 @@ struct _vattr_sp_handle
     vattr_sp *sp;
     struct _vattr_sp_handle *next; /* So we can link them together in the map */
     void *hint;                    /* Hint to the SP */
+    uint64_t rc;
 };
 
 /* Calls made by Service Providers */
@@ -1770,7 +1771,7 @@ is a separate thing in the insterests of stability.
 
  */
 
-#define VARRT_MAP_HASHTABLE_SIZE 10
+#define VARRT_MAP_HASHTABLE_SIZE 32
 
 /* Attribute map oject */
 /* Needs to contain: a linked list of pointers to provider handles handles,
@@ -1867,7 +1868,10 @@ vattr_map_entry_free(vattr_map_entry *vae)
     vattr_sp_handle *list_entry = vae->sp_list;
     while (list_entry != NULL) {
         vattr_sp_handle *next_entry = list_entry->next;
-        slapi_ch_free((void **)&list_entry);
+        if (slapi_atomic_decr_64(&(list_entry->rc), __ATOMIC_RELAXED) == 0) {
+            /* Only free on RC 0 */
+            slapi_ch_free((void **)&list_entry);
+        }
         list_entry = next_entry;
     }
     slapi_ch_free_string(&(vae->type_name));
@@ -2280,6 +2284,17 @@ to handle the calls on it, but return nothing */
  *
  * Better idea, is that regattr should just take the fn pointers
  * and callers never *see* the sp_handle structure at all.
+ *
+ * This leaves us with some quirks today. First: if you have plugin A
+ * and B, A registers attr 1 and B 1 and 2, it's possible that if you
+ * register A1 first, then B1, you have B->A in next. Then when you
+ * register B2, because we take 0==result from map_lookup, we add sp
+ * "as is" to the map. This means that B2 now has the same next to A1
+ * handle. This won't add a bug, because A1 won't be able to service the
+ * attr, but it could cause some head scratching ...
+ *
+ * Again, to fix this, the whole vattr external interface needs a
+ * redesign ... :(
  */
 
 int
@@ -2304,11 +2319,15 @@ vattr_map_sp_insert(char *type_to_add, vattr_sp_handle *sp, void *hint)
         if (found) {
             return 0;
         }
+        /* Increase the ref count of the sphandle */
+        slapi_atomic_incr_64(&(sp->rc), __ATOMIC_RELAXED);
         /* We insert the SP handle into the linked list at the head */
         sp->next = map_entry->sp_list;
         map_entry->sp_list = sp;
     } else {
         /* If not, add it */
+        /* Claim a reference on the sp ... */
+        slapi_atomic_incr_64(&(sp->rc), __ATOMIC_RELAXED);
         map_entry = vattr_map_entry_new(type_to_add, sp, hint);
         if (NULL == map_entry) {
             return ENOMEM;
-- 
2.13.6