3571. [bug] Address race condition in dns_client_startresolve().

[RT #33234]

CHANGES

@@ -1,6 +1,9 @@
 3574.	[doc]		The 'hostname' keyword was missing from server-id
 			description in the named.conf man page. [RT #33476]
 
+3571.	[bug]		Address race condition in dns_client_startresolve().
+			[RT #33234]
+
 	--- 9.9.3 released ---
 
 3568.	[cleanup]	Add a product description line to the version file,

lib/dns/client.c

@@ -1094,11 +1094,23 @@ client_resfind(resctx_t *rctx, dns_fetchevent_t *event) {
 	UNLOCK(&rctx->lock);
 }
 
+
+static void
+suspend(isc_task_t *task, isc_event_t *event) {
+	isc_appctx_t *actx = event->ev_arg;
+
+	UNUSED(task);
+
+	isc_app_ctxsuspend(actx);
+	isc_event_free(&event);
+}
+
 static void
 resolve_done(isc_task_t *task, isc_event_t *event) {
 	resarg_t *resarg = event->ev_arg;
 	dns_clientresevent_t *rev = (dns_clientresevent_t *)event;
 	dns_name_t *name;
+	isc_result_t result;
 
 	UNUSED(task);
 
@@ -1117,8 +1129,16 @@ resolve_done(isc_task_t *task, isc_event_t *event) {
 	if (!resarg->canceled) {
 		UNLOCK(&resarg->lock);
 
-		/* Exit from the internal event loop */
-		isc_app_ctxsuspend(resarg->actx);
+		/*
+		 * We may or may not be running.  isc__appctx_onrun will
+		 * fail if we are currently running otherwise we post a
+		 * action to call isc_app_ctxsuspend when we do start
+		 * running.
+		 */
+		result = isc_app_ctxonrun(resarg->actx, resarg->client->mctx,
+					   task, suspend, resarg->actx);
+		if (result == ISC_R_ALREADYRUNNING)
+			isc_app_ctxsuspend(resarg->actx);
 	} else {
 		/*
 		 * We have already exited from the loop (due to some
@@ -1310,9 +1330,8 @@ dns_client_startresolve(dns_client_t *client, dns_name_t *name,
 	ISC_LIST_APPEND(client->resctxs, rctx, link);
 	UNLOCK(&client->lock);
 
-	client_resfind(rctx, NULL);
-
 	*transp = (dns_clientrestrans_t *)rctx;
+	client_resfind(rctx, NULL);
 
 	return (ISC_R_SUCCESS);
 

lib/isc/app_api.c

@@ -90,6 +90,16 @@ isc_app_ctxrun(isc_appctx_t *ctx) {
 	return (ctx->methods->ctxrun(ctx));
 }
 
+isc_result_t
+isc_app_ctxonrun(isc_appctx_t *ctx, isc_mem_t *mctx,
+		 isc_task_t *task, isc_taskaction_t action,
+	         void *arg)
+{
+	REQUIRE(ISCAPI_APPCTX_VALID(ctx));
+
+	return (ctx->methods->ctxonrun(ctx, mctx, task, action, arg));
+}
+
 isc_result_t
 isc_app_ctxsuspend(isc_appctx_t *ctx) {
 	REQUIRE(ISCAPI_APPCTX_VALID(ctx));

lib/isc/include/isc/app.h

@@ -117,6 +117,9 @@ typedef struct isc_appmethods {
 					isc_socketmgr_t *timermgr);
 	void		(*settimermgr)(isc_appctx_t *ctx,
 				       isc_timermgr_t *timermgr);
+	isc_result_t 	(*ctxonrun)(isc_appctx_t *ctx, isc_mem_t *mctx,
+				    isc_task_t *task, isc_taskaction_t action,
+				    void *arg);
 } isc_appmethods_t;
 
 /*%
@@ -153,10 +156,13 @@ isc_app_start(void);
  *	close to the beginning of the application as possible.
  *
  * Requires:
- *	'ctx' is a valid application context (for app_ctxstart()).
+ *\li	'ctx' is a valid application context (for app_ctxstart()).
  */
 
 isc_result_t
+isc_app_ctxonrun(isc_appctx_t *ctx, isc_mem_t *mctx, isc_task_t *task,
+		 isc_taskaction_t action, void *arg);
+isc_result_t
 isc_app_onrun(isc_mem_t *mctx, isc_task_t *task, isc_taskaction_t action,
 	      void *arg);
 /*!<
@@ -164,6 +170,7 @@ isc_app_onrun(isc_mem_t *mctx, isc_task_t *task, isc_taskaction_t action,
  *
  * Requires:
  *\li	isc_app_start() has been called.
+ *\li	'ctx' is a valid application context (for app_ctxonrun()).
  *
  * Returns:
  *	ISC_R_SUCCESS

lib/isc/unix/app.c

@@ -107,6 +107,11 @@ ISC_APPFUNC_SCOPE void isc__appctx_setsocketmgr(isc_appctx_t *ctx,
 						isc_socketmgr_t *socketmgr);
 ISC_APPFUNC_SCOPE void isc__appctx_settimermgr(isc_appctx_t *ctx,
 					       isc_timermgr_t *timermgr);
+ISC_APPFUNC_SCOPE isc_result_t isc__app_ctxonrun(isc_appctx_t *ctx,
+						 isc_mem_t *mctx,
+					         isc_task_t *task,
+						 isc_taskaction_t action,
+					         void *arg);
 
 /*
  * The application context of this module.  This implementation actually
@@ -148,8 +153,7 @@ static struct {
 	 * The following are defined just for avoiding unused static functions.
 	 */
 #ifndef BIND9
-	void *run, *shutdown, *start, *onrun, *reload, *finish,
-		*block, *unblock;
+	void *run, *shutdown, *start, *reload, *finish, *block, *unblock;
 #endif
 } appmethods = {
 	{
@@ -161,7 +165,8 @@ static struct {
 		isc__app_ctxfinish,
 		isc__appctx_settaskmgr,
 		isc__appctx_setsocketmgr,
-		isc__appctx_settimermgr
+		isc__appctx_settimermgr,
+		isc__app_ctxonrun
 	}
 #ifndef BIND9
 	,
@@ -387,13 +392,22 @@ ISC_APPFUNC_SCOPE isc_result_t
 isc__app_onrun(isc_mem_t *mctx, isc_task_t *task, isc_taskaction_t action,
 	      void *arg)
 {
+	return (isc__app_ctxonrun((isc_appctx_t *)&isc_g_appctx, mctx,
+				  task, action, arg));
+}
+
+isc_result_t
+isc__app_ctxonrun(isc_appctx_t *ctx0, isc_mem_t *mctx, isc_task_t *task,
+		  isc_taskaction_t action, void *arg)
+{
+	isc__appctx_t *ctx = (isc__appctx_t *)ctx0;
 	isc_event_t *event;
 	isc_task_t *cloned_task = NULL;
 	isc_result_t result;
 
-	LOCK(&isc_g_appctx.lock);
+	LOCK(&ctx->lock);
 
-	if (isc_g_appctx.running) {
+	if (ctx->running) {
 		result = ISC_R_ALREADYRUNNING;
 		goto unlock;
 	}
@@ -410,12 +424,12 @@ isc__app_onrun(isc_mem_t *mctx, isc_task_t *task, isc_taskaction_t action,
 		goto unlock;
 	}
 
-	ISC_LIST_APPEND(isc_g_appctx.on_run, event, ev_link);
+	ISC_LIST_APPEND(ctx->on_run, event, ev_link);
 
 	result = ISC_R_SUCCESS;
 
  unlock:
-	UNLOCK(&isc_g_appctx.lock);
+	UNLOCK(&ctx->lock);
 
 	return (result);
 }