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From: Vladislav Shpilevoy <v.shpilevoy@tarantool.org>
To: tarantool-patches@freelists.org,
	Alexander Turenko <alexander.turenko@tarantool.org>
Cc: AKhatskevich <avkhatskevich@tarantool.org>
Subject: [tarantool-patches] Re: [PATCH v2 1/3] lua-yaml: verify arguments count
Date: Fri, 25 Jan 2019 00:26:53 +0300	[thread overview]
Message-ID: <04a54285-aa7c-2726-0077-64c14a40dde6@tarantool.org> (raw)
In-Reply-To: <58ccdb031d0befd0e80d50a4684f5e7a59182062.1548123025.git.alexander.turenko@tarantool.org>

Thanks for the patch!

On 22/01/2019 05:12, Alexander Turenko wrote:
> From: AKhatskevich <avkhatskevich@tarantool.org>
> 
> Added arguments count check for yaml.encode() and decode.decode()

Typo: 'decode.decode' -> 'yaml.decode'.

> functions.
> 
> Without these checks the functions could read garbage outside of a Lua
> stack when called w/o arguments.

Honestly, I do not understand how is it possible. Please,
provide a test for both functions. See my 3 doubts below.

> ---
>   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)) {

1. How could the old code lead to a bug, if there was a
check if the first argument is a string? The second argument
is not used until the next hunk, about which see my next
comment

>   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) {

2. This function never touches anything beyond second value on
the stack, so here lua_gettop(L) > 1 means the same as
lua_gettop(L) == 2 - the second argument exist. Third and next
values do not matter.

>         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)) {

3. Here my reasoning is the same - the previous checking works
as well.

>   usage_error:
>         return luaL_error(L, "Usage: encode(object, {tag_prefix = <string>, "\
>                           "tag_handle = <string>})");
> 

  reply	other threads:[~2019-01-24 21:27 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-22  2:12 [tarantool-patches] [PATCH v2 0/3] lua-yaml null/boolean fixes Alexander Turenko
2019-01-22  2:12 ` [tarantool-patches] [PATCH v2 1/3] lua-yaml: verify arguments count Alexander Turenko
2019-01-24 21:26   ` Vladislav Shpilevoy [this message]
2019-02-05  3:29     ` [tarantool-patches] " Alexander Turenko
2019-02-05 19:36       ` Vladislav Shpilevoy
2019-02-11 13:32         ` Alexander Turenko
2019-02-15 21:28           ` Vladislav Shpilevoy
2019-01-22  2:12 ` [tarantool-patches] [PATCH v2 2/3] lua-yaml: fix boolean/null representation in yaml Alexander Turenko
2019-01-24 21:26   ` [tarantool-patches] " Vladislav Shpilevoy
2019-01-24 21:32     ` Vladislav Shpilevoy
2019-02-05  3:29     ` Alexander Turenko
2019-02-05 19:36       ` Vladislav Shpilevoy
2019-02-15 21:06         ` Vladislav Shpilevoy
2019-02-15 21:23           ` Alexander Turenko
2019-02-18 18:55         ` Alexander Turenko
2019-02-22 15:14           ` Vladislav Shpilevoy
2019-01-22  2:12 ` [tarantool-patches] [PATCH v2 3/3] lua-yaml: treat an empty document/value as null Alexander Turenko
2019-01-24 21:26   ` [tarantool-patches] " Vladislav Shpilevoy
2019-02-05  3:30     ` Alexander Turenko
2019-01-24 21:26 ` [tarantool-patches] Re: [PATCH v2 0/3] lua-yaml null/boolean fixes Vladislav Shpilevoy
2019-02-25 11:27 ` Kirill Yukhin
2019-03-05 16:40   ` Alexander Turenko
2019-03-06  7:21     ` Kirill Yukhin

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