linux-kernel - Re: [PATCH] security: keys: add __randomize_layout to keyring_search

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Date:   Wed, 18 May 2022 13:25:28 -0700
From:   Kees Cook <keescook@...omium.org>
To:     "GONG, Ruiqi" <gongruiqi1@...wei.com>
Cc:     David Howells <dhowells@...hat.com>,
        Jarkko Sakkinen <jarkko@...nel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E . Hallyn" <serge@...lyn.com>, keyrings@...r.kernel.org,
        linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org,
        Wang Weiyang <wangweiyang2@...wei.com>,
        Xiu Jianfeng <xiujianfeng@...wei.com>
Subject: Re: [PATCH] security: keys: add __randomize_layout to
 keyring_search_context

On Wed, May 18, 2022 at 09:18:41AM +0000, GONG, Ruiqi wrote:
> Struct keyring_search_context contains a pointer to `struct cred`, which
> is a security-critical structure and whose layout is randomized already.
> Apply __randomize_layout to struct keyring_search_context as well, as
> suggested in [1].
> 
> [1]: https://github.com/KSPP/linux/issues/188
> 
> Signed-off-by: GONG, Ruiqi <gongruiqi1@...wei.com>

Seems reasonable to me; it's an entirely internal structure.

Reviewed-by: Kees Cook <keescook@...omium.org>

> ---
>  security/keys/internal.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/security/keys/internal.h b/security/keys/internal.h
> index 9b9cf3b6fcbb..3e3def5fbaa4 100644
> --- a/security/keys/internal.h
> +++ b/security/keys/internal.h
> @@ -136,7 +136,7 @@ struct keyring_search_context {
>  	bool			possessed;
>  	key_ref_t		result;
>  	time64_t		now;
> -};
> +} __randomize_layout;
>  
>  extern bool key_default_cmp(const struct key *key,
>  			    const struct key_match_data *match_data);
> -- 
> 2.17.1
> 

-- 
Kees Cook