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