linux-kernel - Re: [PATCH v2] LSM: Convert security_hook_heads into explicit array of struct list

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Message-ID: <alpine.LRH.2.20.1705302025110.31018@namei.org>
Date:   Tue, 30 May 2017 20:32:02 +1000 (AEST)
From:   James Morris <jmorris@...ei.org>
To:     Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
cc:     linux-security-module@...r.kernel.org,
        linux-kernel@...r.kernel.org, kernel-hardening@...ts.openwall.com,
        Casey Schaufler <casey@...aufler-ca.com>,
        Christoph Hellwig <hch@...radead.org>,
        Igor Stoppa <igor.stoppa@...wei.com>,
        James Morris <james.l.morris@...cle.com>,
        Kees Cook <keescook@...omium.org>,
        Paul Moore <paul@...l-moore.com>,
        Stephen Smalley <sds@...ho.nsa.gov>
Subject: Re: [PATCH v2] LSM: Convert security_hook_heads into explicit array
 of struct list_head

On Mon, 29 May 2017, Tetsuo Handa wrote:

> Igor proposed a sealable memory allocator, and the LSM hooks
> ("struct security_hook_heads security_hook_heads" and
> "struct security_hook_list ...[]") will benefit from that allocator via
> protection using set_memory_ro()/set_memory_rw(), and that allocator
> will remove CONFIG_SECURITY_WRITABLE_HOOKS config option. Thus, we will
> likely be moving to that direction.
> 
> This means that these structures will be allocated at run time using
> that allocator, and therefore the address of these structures will be
> determined at run time rather than compile time.
> 
> But currently, LSM_HOOK_INIT() macro depends on the address of
> security_hook_heads being known at compile time. If we use an enum
> so that LSM_HOOK_INIT() macro does not need to know absolute address of
> security_hook_heads, it will help us to use that allocator for LSM hooks.
> 

This seems like pointless churn in security-critical code in anticipation 
of features which are still in development and may not be adopted.

Is there a compelling reason to merge this now? (And I don't mean worrying 
about non-existent compliers).



-- 
James Morris
<jmorris@...ei.org>