From 8faf8490e518315a8eff17a76b019debe48104b4 Mon Sep 17 00:00:00 2001 From: Mark Pulford Date: Tue, 17 Jan 2012 23:28:10 +1030 Subject: Fix Lua C function stack overflow during encoding Ensure there are enough Lua stack slots available before descending into another table during encoding. This fixes a segfault when encoding deeply nested tables. This bug wasn't noticed earlier due to the previous limit of 20 nested tables. --- lua_cjson.c | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'lua_cjson.c') diff --git a/lua_cjson.c b/lua_cjson.c index 00fa2dd..4a2ce0f 100644 --- a/lua_cjson.c +++ b/lua_cjson.c @@ -564,12 +564,17 @@ static int lua_array_length(lua_State *l, json_config_t *cfg, strbuf_t *json) static void json_check_encode_depth(lua_State *l, json_config_t *cfg, int current_depth, strbuf_t *json) { - if (current_depth > cfg->encode_max_depth) { - if (!cfg->encode_keep_buffer) - strbuf_free(json); - luaL_error(l, "Cannot serialise, excessive nesting (%d)", - current_depth); - } + /* Ensure there are enough slots free to traverse a table (key, value). + * luaL_error() and other Lua API functions use space from the + * "EXTRA_STACK" reserve. */ + if (current_depth <= cfg->encode_max_depth && lua_checkstack(l, 2)) + return; + + if (!cfg->encode_keep_buffer) + strbuf_free(json); + + luaL_error(l, "Cannot serialise, excessive nesting (%d)", + current_depth); } static void json_append_data(lua_State *l, json_config_t *cfg, @@ -692,9 +697,9 @@ static void json_append_data(lua_State *l, json_config_t *cfg, strbuf_append_mem(json, "false", 5); break; case LUA_TTABLE: - len = lua_array_length(l, cfg, json); current_depth++; json_check_encode_depth(l, cfg, current_depth, json); + len = lua_array_length(l, cfg, json); if (len > 0) json_append_array(l, cfg, current_depth, json, len); else -- cgit v1.2.3-55-g6feb