Make library init threadsafe

Fixes #584

Signed-off-by: Ondřej Kuzník <[email protected]>

lib/common.c

@@ -197,7 +197,7 @@ void sasl_set_mutex(sasl_mutex_alloc_t *n,
 {
     /* Disallow mutex function changes once sasl_client_init
        and/or sasl_server_init is called */
-    if (_sasl_server_cleanup_hook || _sasl_client_cleanup_hook) {
+    if (free_mutex) {
 	return;
     }
 
@@ -207,6 +207,25 @@ void sasl_set_mutex(sasl_mutex_alloc_t *n,
     _sasl_mutex_utils.free=d;
 }
 
+void _sasl_mutex_init(void)
+{
+    if (_sasl_mutex_utils.alloc != &sasl_mutex_alloc) {
+	free_mutex = _sasl_mutex_utils.alloc();
+	return;
+    }
+
+#if defined(HAVE_PTHREAD)
+    free_mutex = &static_mutex;
+#elif defined(HAVE_NT_THREADS)
+    HANDLE p = CreateMutex(NULL, 0, NULL);
+    if (InterlockedCompareExchangePointer((PVOID*)&free_mutex, (PVOID)p, NULL) != NULL)
+	CloseHandle(p);
+#else
+    free_mutex = _sasl_mutex_utils.alloc();
+#endif
+    return;
+}
+
 /* copy a string to malloced memory */
 int _sasl_strdup(const char *in, char **out, size_t *outlen)
 {
@@ -831,34 +850,40 @@ int _sasl_common_init(sasl_global_callbacks_t *global_callbacks)
 {
     int result;
 
-    /* The last specified global callback always wins */
-    if (sasl_global_utils != NULL) {
-	sasl_utils_t * global_utils = (sasl_utils_t *)sasl_global_utils;
+    if (!free_mutex) {
+	_sasl_mutex_init();
+	if (!free_mutex) {
+	    return SASL_FAIL;
+	}
+    }
+
+    result = sasl_MUTEX_LOCK(free_mutex);
+    if (result != SASL_OK) return SASL_FAIL;
+
+    /* Just update global callback if we are already initialized */
+    if (sasl_global_utils) {
+	sasl_utils_t *global_utils = (sasl_utils_t *)sasl_global_utils;
 	global_utils->getopt = &_sasl_global_getopt;
 	global_utils->getopt_context = global_callbacks;
-    }
 
-    /* Do nothing if we are already initialized */
-    if (free_mutex) {
+	sasl_MUTEX_UNLOCK(free_mutex);
 	return SASL_OK;
-    }
-
-    /* Setup the global utilities */
-    if(!sasl_global_utils) {
+    } else {
 	sasl_global_utils = _sasl_alloc_utils(NULL, global_callbacks);
-	if(sasl_global_utils == NULL) return SASL_NOMEM;
+	if (sasl_global_utils == NULL) {
+	    sasl_MUTEX_UNLOCK(free_mutex);
+	    return SASL_NOMEM;
+	}
     }
 
     /* Init the canon_user plugin */
     result = sasl_canonuser_add_plugin("INTERNAL", internal_canonuser_init);
-    if(result != SASL_OK) return result;    
-
-    if (!free_mutex) {
-	free_mutex = sasl_MUTEX_ALLOC();
+    if (result != SASL_OK) {
+	result = SASL_FAIL;
     }
-    if (!free_mutex) return SASL_FAIL;
 
-    return SASL_OK;
+    sasl_MUTEX_UNLOCK(free_mutex);
+    return result;
 }
 
 /* dispose connection state, sets it to NULL
@@ -874,7 +899,7 @@ void sasl_dispose(sasl_conn_t **pconn)
   /* serialize disposes. this is necessary because we can't
      dispose of conn->mutex if someone else is locked on it */
   if (!free_mutex) {
-      free_mutex = sasl_MUTEX_ALLOC();
+      _sasl_mutex_init();
       if (!free_mutex) return;
   }