[tarantool-patches] [PATCH v2 1/3] lua-yaml: verify arguments count

[Alexander Turenko <alexander.turenko@tarantool.org>]

From: AKhatskevich <avkhatskevich@tarantool.org>

Added arguments count check for yaml.encode() and decode.decode()
functions.

Without these checks the functions could read garbage outside of a Lua
stack when called w/o arguments.
---
 third_party/lua-yaml/lyaml.cc | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/third_party/lua-yaml/lyaml.cc b/third_party/lua-yaml/lyaml.cc
index c6d118a79..9b07992d8 100644
--- a/third_party/lua-yaml/lyaml.cc
+++ b/third_party/lua-yaml/lyaml.cc
@@ -400,7 +400,8 @@ static void load(struct lua_yaml_loader *loader) {
  */
 static int l_load(lua_State *L) {
    struct lua_yaml_loader loader;
-   if (! lua_isstring(L, 1)) {
+   int top = lua_gettop(L);
+   if (!(top == 1 || top == 2) || !lua_isstring(L, 1)) {
 usage_error:
       return luaL_error(L, "Usage: yaml.decode(document, "\
                         "[{tag_only = boolean}])");
@@ -416,7 +417,7 @@ usage_error:
       return luaL_error(L, OOM_ERRMSG);
    yaml_parser_set_input_string(&loader.parser, (yaml_char_t *) document, len);
    bool tag_only;
-   if (lua_gettop(L) > 1) {
+   if (lua_gettop(L) == 2) {
       if (! lua_istable(L, 2))
          goto usage_error;
       lua_getfield(L, 2, "tag_only");
@@ -794,7 +795,7 @@ error:
 static int l_dump(lua_State *L) {
    struct luaL_serializer *serializer = luaL_checkserializer(L);
    int top = lua_gettop(L);
-   if (top > 2) {
+   if (!(top == 1 || top == 2)) {
 usage_error:
       return luaL_error(L, "Usage: encode(object, {tag_prefix = <string>, "\
                         "tag_handle = <string>})");
-- 
2.20.1