linux-kernel - Re: [PATCH v2] module: Harden STRICT_MODULE

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Date:   Wed, 8 Apr 2020 18:20:42 +0200
From:   Jessica Yu <jeyu@...nel.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
        keescook@...omium.org, Josh Poimboeuf <jpoimboe@...hat.com>,
        Miroslav Benes <mbenes@...e.cz>
Subject: Re: [PATCH v2] module: Harden STRICT_MODULE_RWX

+++ Peter Zijlstra [08/04/20 17:57 +0200]:
[..snip..]
>> Just to clarify, did we want to enforce this only when
>> CONFIG_STRICT_MODULE_RWX=y?  Because here it's still in the
>> CONFIG_ARCH_HAS_STRICT_MODULE_RWX block.
>>
>> Unfortunately, when we add module_enforce_rwx_sections() in the
>> CONFIG_STRICT_MODULE_RWX block, we'll need two empty stubs, one for
>> !CONFIG_ARCH_HAS_STRICT_MODULE_RWX and one for !CONFIG_STRICT_MODULE_RWX.
>>
>> This is because the CONFIG_STRICT_MODULE_RWX block is currently nested
>> within ARCH_HAS_STRICT_MODULE_RWX :/
>
>Yeah, so the primary reason it's under that ARCH_HAS thing is indeed the
>mess and the extra stub required (I'm a lazy sod at times).

Heh :-)

>I then rationalized this decision to myself that having it under
>ARCH_HAS give a more consistent module loading behaviour.
>
>But I really don't care too much, my most my .config's have
>CONFIG_MODULE=n, and the ones that do not very much have the STRICT_RWX
>set.
>
>Put it where you think it's best.

I don't really mind either way, but my gut tells me I should just move
that hunk under STRICT_MODULE_RWX just to be consistent with STRICT
vs. non STRICT semantics. No need to respin, I'll rebase after I queue
the other patch.

Thanks!

Jessica