From: Vladimír Čunát <vladimir.cunat@nic.cz>
Date: Mon, 6 May 2019 11:00:07 +0000 (+0200)
Subject: lua event.*: better safety
X-Git-Tag: v4.1.0~21^2~7
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=63f5cb4dfbfd8fd2932fb8ec64007fdac58af0b7;p=thirdparty%2Fknot-resolver.git

lua event.*: better safety

... when called with bad parameters, and restructure the code a bit.
Note: uv_timer_start() is documented to be OK on active timers.
---

diff --git a/daemon/bindings/event.c b/daemon/bindings/event.c
index 32723a118..a964683bd 100644
--- a/daemon/bindings/event.c
+++ b/daemon/bindings/event.c
@@ -125,18 +125,20 @@ static int event_cancel(lua_State *L)
 
 	/* Fetch event if it exists */
 	lua_rawgeti(L, LUA_REGISTRYINDEX, lua_tointeger(L, 1));
-	if (!lua_istable(L, -1)) {
-		lua_pushboolean(L, false);
-		return 1;
-	}
+	bool ok = lua_istable(L, -1);
 
 	/* Close the timer */
-	lua_rawgeti(L, -1, 2);
-	uv_handle_t *timer = *(uv_handle_t **)lua_touserdata(L, -1);
-	if (!uv_is_closing(timer)) {
-		uv_close(timer, (uv_close_cb) event_free);
+	uv_handle_t **timer_pp = NULL;
+	if (ok) {
+		lua_rawgeti(L, -1, 2);
+		timer_pp = lua_touserdata(L, -1);
+		ok = timer_pp && *timer_pp;
+		/* That have been sufficient safety checks, hopefully. */
+	}
+	if (ok && !uv_is_closing(*timer_pp)) {
+		uv_close(*timer_pp, (uv_close_cb)event_free);
 	}
-	lua_pushboolean(L, true);
+	lua_pushboolean(L, ok);
 	return 1;
 }
 
@@ -148,26 +150,25 @@ static int event_reschedule(lua_State *L)
 
 	/* Fetch event if it exists */
 	lua_rawgeti(L, LUA_REGISTRYINDEX, lua_tointeger(L, 1));
-	if (!lua_istable(L, -1)) {
-		lua_pushboolean(L, false);
-		return 1;
-	}
+	bool ok = lua_istable(L, -1);
 
 	/* Reschedule the timer */
-	lua_rawgeti(L, -1, 2);
-	uv_handle_t *timer = *(uv_handle_t **)lua_touserdata(L, -1);
-	if (!uv_is_closing(timer)) {
-		if (uv_is_active(timer)) {
-			uv_timer_stop((uv_timer_t *)timer);
-		}
-		int ret = uv_timer_start((uv_timer_t *)timer, event_callback, lua_tointeger(L, 2), 0);
+	uv_handle_t **timer_pp = NULL;
+	if (ok) {
+		lua_rawgeti(L, -1, 2);
+		timer_pp = lua_touserdata(L, -1);
+		ok = timer_pp && *timer_pp;
+		/* That have been sufficient safety checks, hopefully. */
+	}
+	if (ok && !uv_is_closing(*timer_pp)) {
+		int ret = uv_timer_start((uv_timer_t *)*timer_pp,
+				event_callback, lua_tointeger(L, 2), 0);
 		if (ret != 0) {
-			event_cancel(L);
-			lua_pushboolean(L, false);
-			return 1;
+			uv_close(*timer_pp, (uv_close_cb)event_free);
+			ok = false;
 		}
 	}
-	lua_pushboolean(L, true);
+	lua_pushboolean(L, ok);
 	return 1;
 }