linux-kernel - Re: [PATCH 2/2] arm: apply more __ro_after

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Message-ID: <CAGXu5j+9saxwnKTK_vdnLCuXdbvUqQWXkbxOu8QrzB9SHmQGYA@mail.gmail.com>
Date:	Wed, 10 Aug 2016 11:32:07 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Russell King - ARM Linux <linux@...linux.org.uk>
Cc:	"kernel-hardening@...ts.openwall.com" 
	<kernel-hardening@...ts.openwall.com>,
	linux-arch <linux-arch@...r.kernel.org>,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>,
	"x86@...nel.org" <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mathias Krause <minipli@...glemail.com>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH 2/2] arm: apply more __ro_after_init

On Wed, Aug 10, 2016 at 2:43 AM, Russell King - ARM Linux
<linux@...linux.org.uk> wrote:
> On Fri, Jun 03, 2016 at 11:40:24AM -0700, Kees Cook wrote:
>> @@ -1309,16 +1309,11 @@ void __init arm_mm_memblock_reserve(void)
>>   * Any other function or debugging method which may touch any device _will_
>>   * crash the kernel.
>>   */
>> +static char vectors[PAGE_SIZE * 2] __ro_after_init __aligned(PAGE_SIZE);
>>  static void __init devicemaps_init(const struct machine_desc *mdesc)
>>  {
>>       struct map_desc map;
>>       unsigned long addr;
>> -     void *vectors;
>> -
>> -     /*
>> -      * Allocate the vector page early.
>> -      */
>> -     vectors = early_alloc(PAGE_SIZE * 2);
>
> This one is not appropriate.  We _do_ write to these pages after init
> for FIQ handler updates.  See set_fiq_handler().

Ah, interesting. I guess none of that hardware is being tested on
linux-next. I'll drop that chunk and resubmit.

Thanks!

-Kees

-- 
Kees Cook
Nexus Security