linux-kernel - Re: [kernel-hardening] Re: [PATCH v2 05/20] randstruct: Whitelist struct security_hook

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Message-ID: <CAGXu5jJYvHFy2dh90ZKoGaBvFDUThd2kQqyWG3zjXxTSW3ihjQ@mail.gmail.com>
Date:   Sat, 27 May 2017 17:43:02 -0700
From:   Kees Cook <keescook@...omium.org>
To:     Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Cc:     Christoph Hellwig <hch@...radead.org>,
        "kernel-hardening@...ts.openwall.com" 
        <kernel-hardening@...ts.openwall.com>,
        James Morris <james.l.morris@...cle.com>,
        Laura Abbott <labbott@...hat.com>,
        "x86@...nel.org" <x86@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        linux-security-module <linux-security-module@...r.kernel.org>
Subject: Re: [kernel-hardening] Re: [PATCH v2 05/20] randstruct: Whitelist
 struct security_hook_heads cast

On Sat, May 27, 2017 at 3:04 PM, Tetsuo Handa
<penguin-kernel@...ove.sakura.ne.jp> wrote:
> Kees Cook wrote:
>> On Sat, May 27, 2017 at 1:41 AM, Christoph Hellwig <hch@...radead.org> wrote:
>> > On Fri, May 26, 2017 at 01:17:09PM -0700, Kees Cook wrote:
>> >> The LSM initialization routines walk security_hook_heads as an array
>> >> of struct list_head instead of via names to avoid a ton of needless
>> >> source. Whitelist this to avoid the false positive warning from the
>> >> plugin:
>> >
>> > I think this crap just needs to be fixed properly.  If not it almost
>> > defeats the protections as the "security" ops are just about everywhere.
>>
>> There's nothing unsafe about 3dfc9b02864b19f4dab376f14479ee4ad1de6c9e,
>> it just avoids tons of needless code. Tetsuo has some other ideas for
>> cleaning it up further, but I don't like it because it removes
>> compile-time verification of function types.
>
> Excuse me, but why you think that compile-time verification of function
> types is removed?
>
> -       { .head = &security_hook_heads.HEAD, .hook = { .HEAD = HOOK } }
> +       { .idx = LSM_##HEAD, .hook = { .HEAD = HOOK } }
>
> This change removes dependency on absolute address of security_hook_heads
> being known at compile-time. If function types of .hook.HEAD and HOOK
> mismatches, the compiler can still warn it.

Sorry, misremembered, that was the other patch. I'll go review this
current one...

-Kees

-- 
Kees Cook
Pixel Security