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

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Message-ID: <20160810094339.GK1041@n2100.armlinux.org.uk>
Date:	Wed, 10 Aug 2016 10:43:39 +0100
From:	Russell King - ARM Linux <linux@...linux.org.uk>
To:	Kees Cook <keescook@...omium.org>
Cc:	kernel-hardening@...ts.openwall.com, linux-arch@...r.kernel.org,
	Ard Biesheuvel <ard.biesheuvel@...aro.org>, x86@...nel.org,
	linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Mathias Krause <minipli@...glemail.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 2/2] arm: apply more __ro_after_init

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().

-- 
RMK's Patch system: http://www.armlinux.org.uk/developer/patches/
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