1 files changed, 104 insertions, 89 deletions

diff --git a/main/loader.c b/main/loader.c
index 23a29d994..f204a865c 100644
--- a/main/loader.c
+++ b/main/loader.c
@@ -167,38 +167,51 @@ static int do_full_reload = 0;
 
 static AST_DLLIST_HEAD_STATIC(reload_queue, reload_queue_item);
 
-/* when dynamic modules are being loaded, ast_module_register() will
-   need to know what filename the module was loaded from while it
-   is being registered
-*/
+/*!
+ * \internal
+ *
+ * This variable is set by load_dynamic_module so ast_module_register
+ * can know what pointer is being registered.
+ *
+ * This is protected by the module_list lock.
+ */
 static struct ast_module *resource_being_loaded;
 
-/* XXX: should we check for duplicate resource names here? */
-
+/*!
+ * \internal
+ * \brief Used by AST_MODULE_INFO to register with the module loader.
+ *
+ * This function is automatically called when each module is opened.
+ * It must never be used from outside AST_MODULE_INFO.
+ */
 void ast_module_register(const struct ast_module_info *info)
 {
-	struct ast_module *mod = resource_being_loaded;
+	struct ast_module *mod;
+
+	/*
+	 * This lock protects resource_being_loaded as well as the module
+	 * list.  Normally we already have a lock on module_list when we
+	 * begin the load but locking again from here prevents corruption
+	 * if an asterisk module is dlopen'ed from outside the module loader.
+	 */
+	AST_DLLIST_LOCK(&module_list);
+	mod = resource_being_loaded;
+	if (!mod) {
+		AST_DLLIST_UNLOCK(&module_list);
+		return;
+	}
 
 	ast_debug(5, "Registering module %s\n", info->name);
 
+	/* This tells load_dynamic_module that we're registered. */
+	resource_being_loaded = NULL;
+
 	mod->info = info;
 	if (ast_opt_ref_debug) {
 		mod->ref_debug = ao2_t_alloc(0, NULL, info->name);
 	}
 	AST_LIST_HEAD_INIT(&mod->users);
 
-	/* during startup, before the loader has been initialized,
-	   there are no threads, so there is no need to take the lock
-	   on this list to manipulate it. it is also possible that it
-	   might be unsafe to use the list lock at that point... so
-	   let's avoid it altogether
-	*/
-	AST_DLLIST_LOCK(&module_list);
-	/* it is paramount that the new entry be placed at the tail of
-	   the list, otherwise the code that uses dlopen() to load
-	   dynamic modules won't be able to find out if the module it
-	   just opened was registered or failed to load
-	*/
 	AST_DLLIST_INSERT_TAIL(&module_list, mod, entry);
 	AST_DLLIST_UNLOCK(&module_list);
 
@@ -206,6 +219,13 @@ void ast_module_register(const struct ast_module_info *info)
 	*((struct ast_module **) &(info->self)) = mod;
 }
 
+static void module_destroy(struct ast_module *mod)
+{
+	AST_LIST_HEAD_DESTROY(&mod->users);
+	ao2_cleanup(mod->ref_debug);
+	ast_free(mod);
+}
+
 void ast_module_unregister(const struct ast_module_info *info)
 {
 	struct ast_module *mod = NULL;
@@ -226,9 +246,7 @@ void ast_module_unregister(const struct ast_module_info *info)
 
 	if (mod) {
 		ast_debug(5, "Unregistering module %s\n", info->name);
-		AST_LIST_HEAD_DESTROY(&mod->users);
-		ao2_cleanup(mod->ref_debug);
-		ast_free(mod);
+		module_destroy(mod);
 	}
 }
 
@@ -502,92 +520,91 @@ static enum ast_module_load_result load_resource(const char *resource_name, unsi
 
 #define MODULE_LOCAL_ONLY (void *)-1
 
-static struct ast_module *load_dynamic_module(const char *resource_in, unsigned int global_symbols_only, unsigned int suppress_logging, struct ast_heap *resource_heap)
+/*!
+ * \internal
+ * \brief Attempt to dlopen a module.
+ *
+ * \param resource_in The module name to load.
+ * \param so_ext ".so" or blank if ".so" is already part of resource_in.
+ * \param filename Passed directly to dlopen.
+ * \param flags Passed directly to dlopen.
+ * \param suppress_logging Do not log any error from dlopen.
+ *
+ * \return Pointer to opened module, NULL on error.
+ *
+ * \warning module_list must be locked before calling this function.
+ */
+static struct ast_module *load_dlopen(const char *resource_in, const char *so_ext,
+	const char *filename, int flags, unsigned int suppress_logging)
 {
-	char fn[PATH_MAX] = "";
-	void *lib = NULL;
 	struct ast_module *mod;
-	unsigned int wants_global;
-	int space;	/* room needed for the descriptor */
-	int missing_so = 0;
-
-	space = sizeof(*resource_being_loaded) + strlen(resource_in) + 1;
-	if (strcasecmp(resource_in + strlen(resource_in) - 3, ".so")) {
-		missing_so = 1;
-		space += 3;	/* room for the extra ".so" */
-	}
 
-	snprintf(fn, sizeof(fn), "%s/%s%s", ast_config_AST_MODULE_DIR, resource_in, missing_so ? ".so" : "");
+	ast_assert(!resource_being_loaded);
 
-	/* make a first load of the module in 'quiet' mode... don't try to resolve
-	   any symbols, and don't export any symbols. this will allow us to peek into
-	   the module's info block (if available) to see what flags it has set */
-
-	resource_being_loaded = ast_calloc(1, space);
-	if (!resource_being_loaded)
+	mod = ast_calloc(1, sizeof(*mod) + strlen(resource_in) + strlen(so_ext) + 1);
+	if (!mod) {
 		return NULL;
-	strcpy(resource_being_loaded->resource, resource_in);
-	if (missing_so)
-		strcat(resource_being_loaded->resource, ".so");
+	}
+
+	sprintf(mod->resource, "%s%s", resource_in, so_ext); /* safe */
 
-	if (!(lib = dlopen(fn, RTLD_LAZY | RTLD_GLOBAL))) {
-		if (!suppress_logging) {
+	resource_being_loaded = mod;
+	mod->lib = dlopen(filename, flags);
+	if (resource_being_loaded) {
+		resource_being_loaded = NULL;
+		if (mod->lib) {
+			ast_log(LOG_ERROR, "Module '%s' did not register itself during load\n", resource_in);
+			logged_dlclose(resource_in, mod->lib);
+		} else if (!suppress_logging) {
 			ast_log(LOG_WARNING, "Error loading module '%s': %s\n", resource_in, dlerror());
 		}
-		ast_free(resource_being_loaded);
-		return NULL;
-	}
+		ast_free(mod);
 
-	/* the dlopen() succeeded, let's find out if the module
-	   registered itself */
-	/* note that this will only work properly as long as
-	   ast_module_register() (which is called by the module's
-	   constructor) places the new module at the tail of the
-	   module_list
-	*/
-	if (resource_being_loaded != (mod = AST_DLLIST_LAST(&module_list))) {
-		ast_log(LOG_WARNING, "Module '%s' did not register itself during load\n", resource_in);
-		/* no, it did not, so close it and return */
-		logged_dlclose(resource_in, lib);
-		/* note that the module's destructor will call ast_module_unregister(),
-		   which will free the structure we allocated in resource_being_loaded */
 		return NULL;
 	}
 
-	wants_global = ast_test_flag(mod->info, AST_MODFLAG_GLOBAL_SYMBOLS);
+	return mod;
+}
 
-	/* if we are being asked only to load modules that provide global symbols,
-	   and this one does not, then close it and return */
-	if (global_symbols_only && !wants_global) {
-		logged_dlclose(resource_in, lib);
-		return MODULE_LOCAL_ONLY;
+static struct ast_module *load_dynamic_module(const char *resource_in, unsigned int global_symbols_only, unsigned int suppress_logging, struct ast_heap *resource_heap)
+{
+	char fn[PATH_MAX];
+	struct ast_module *mod;
+	size_t resource_in_len = strlen(resource_in);
+	int exports_globals;
+	const char *so_ext = "";
+
+	if (resource_in_len < 4 || strcasecmp(resource_in + resource_in_len - 3, ".so")) {
+		so_ext = ".so";
 	}
 
-	logged_dlclose(resource_in, lib);
-	resource_being_loaded = NULL;
+	snprintf(fn, sizeof(fn), "%s/%s%s", ast_config_AST_MODULE_DIR, resource_in, so_ext);
 
-	/* start the load process again */
-	resource_being_loaded = ast_calloc(1, space);
-	if (!resource_being_loaded)
-		return NULL;
-	strcpy(resource_being_loaded->resource, resource_in);
-	if (missing_so)
-		strcat(resource_being_loaded->resource, ".so");
+	/* Try loading in quiet mode first with flags to export global symbols.
+	 * If the module does not want to export globals we will close and reopen. */
+	mod = load_dlopen(resource_in, so_ext, fn,
+		global_symbols_only ? RTLD_LAZY | RTLD_GLOBAL : RTLD_NOW | RTLD_LOCAL,
+		suppress_logging);
 
-	if (!(lib = dlopen(fn, wants_global ? RTLD_LAZY | RTLD_GLOBAL : RTLD_NOW | RTLD_LOCAL))) {
-		ast_log(LOG_WARNING, "Error loading module '%s': %s\n", resource_in, dlerror());
-		ast_free(resource_being_loaded);
+	if (!mod) {
 		return NULL;
 	}
 
-	/* since the module was successfully opened, and it registered itself
-	   the previous time we did that, we're going to assume it worked this
-	   time too :) */
+	exports_globals = ast_test_flag(mod->info, AST_MODFLAG_GLOBAL_SYMBOLS);
+	if ((global_symbols_only && exports_globals) || (!global_symbols_only && !exports_globals)) {
+		/* The first dlopen had the correct flags. */
+		return mod;
+	}
 
-	AST_DLLIST_LAST(&module_list)->lib = lib;
-	resource_being_loaded = NULL;
+	/* Close the module so we can reopen with correct flags. */
+	logged_dlclose(resource_in, mod->lib);
+	if (global_symbols_only) {
+		return MODULE_LOCAL_ONLY;
+	}
 
-	return AST_DLLIST_LAST(&module_list);
+	return load_dlopen(resource_in, so_ext, fn,
+		exports_globals ? RTLD_LAZY | RTLD_GLOBAL : RTLD_NOW | RTLD_LOCAL,
+		0);
 }
 
 int modules_shutdown(void)
@@ -621,9 +638,7 @@ int modules_shutdown(void)
 				ast_verb(1, "Unloading %s\n", mod->resource);
 				mod->info->unload();
 			}
-			AST_LIST_HEAD_DESTROY(&mod->users);
-			ao2_cleanup(mod->ref_debug);
-			ast_free(mod);
+			module_destroy(mod);
 			somethingchanged = 1;
 		}
 		AST_DLLIST_TRAVERSE_BACKWARDS_SAFE_END;