Re: [PATCH 2/2] randstruct: remove dead code in is_pure_ops_struct()

From: Kees Cook <keescook@chromium.org>
To: Joonwon Kang <kjw1627@gmail.com>
Cc: re.emese@gmail.com, kernel-hardening@lists.openwall.com,
	linux-kernel@vger.kernel.org, kernel-janitors@vger.kernel.org,
	jinb.park7@gmail.com
Subject: Re: [PATCH 2/2] randstruct: remove dead code in is_pure_ops_struct()
Date: Wed, 31 Jul 2019 12:59:30 -0700	[thread overview]
Message-ID: <201907311259.D485EED2B7@keescook> (raw)
In-Reply-To: <281a65cc361512e3dc6c5deffa324f800eb907be.1564595346.git.kjw1627@gmail.com>

On Thu, Aug 01, 2019 at 03:01:49AM +0900, Joonwon Kang wrote:
> Recursive declaration for struct which has member of the same struct
> type, for example,
> 
> struct foo {
>     struct foo f;
>     ...
> };
> 
> is not allowed. So, it is unnecessary to check if a struct has this
> kind of member.

Is that the only case where this loop could happen? Seems also safe to
just leave it as-is...

-Kees

> 
> Signed-off-by: Joonwon Kang <kjw1627@gmail.com>
> ---
>  scripts/gcc-plugins/randomize_layout_plugin.c | 3 ---
>  1 file changed, 3 deletions(-)
> 
> diff --git a/scripts/gcc-plugins/randomize_layout_plugin.c b/scripts/gcc-plugins/randomize_layout_plugin.c
> index bd29e4e7a524..e14efe23e645 100644
> --- a/scripts/gcc-plugins/randomize_layout_plugin.c
> +++ b/scripts/gcc-plugins/randomize_layout_plugin.c
> @@ -440,9 +440,6 @@ static int is_pure_ops_struct(const_tree node)
>  		const_tree fieldtype = get_field_type(field);
>  		enum tree_code code = TREE_CODE(fieldtype);
>  
> -		if (node == fieldtype)
> -			continue;
> -
>  		if (code == RECORD_TYPE || code == UNION_TYPE) {
>  			if (!is_pure_ops_struct(fieldtype))
>  				return 0;
> -- 
> 2.17.1
> 

-- 
Kees Cook