linux-kernel - Re: [PATCH] dma-debug: Switch check from _text to

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Date:	Mon, 4 Jan 2016 11:15:44 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Laura Abbott <labbott@...oraproject.org>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Russell King <linux@....linux.org.uk>,
	LKML <linux-kernel@...r.kernel.org>,
	Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH] dma-debug: Switch check from _text to _stext

On Mon, Jan 4, 2016 at 10:48 AM, Laura Abbott <labbott@...oraproject.org> wrote:
> From include/asm-generic/sections.h:
>
> /*
>  * Usage guidelines:
>  * _text, _data: architecture specific, don't use them in
>  * arch-independent code
>  * [_stext, _etext]: contains .text.* sections, may also contain
>  * .rodata.*
>  *                   and/or .init.* sections
>
> _text is not guaranteed across architectures. Architectures such as ARM
> may reuse parts which are not actually text and erroneously trigger a bug.
> Switch to using _stext which is guaranteed to contain text sections.
>
> Signed-off-by: Laura Abbott <labbott@...oraproject.org>

Reviewed-by: Kees Cook <keescook@...omium.org>

-Kees

> ---
> Came out of https://lkml.kernel.org/g/<567B1176.4000106@...hat.com>
> ---
>  lib/dma-debug.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/lib/dma-debug.c b/lib/dma-debug.c
> index d34bd24..4a1515f 100644
> --- a/lib/dma-debug.c
> +++ b/lib/dma-debug.c
> @@ -1181,7 +1181,7 @@ static inline bool overlap(void *addr, unsigned long len, void *start, void *end
>
>  static void check_for_illegal_area(struct device *dev, void *addr, unsigned long len)
>  {
> -       if (overlap(addr, len, _text, _etext) ||
> +       if (overlap(addr, len, _stext, _etext) ||
>             overlap(addr, len, __start_rodata, __end_rodata))
>                 err_printk(dev, NULL, "DMA-API: device driver maps memory from kernel text or rodata [addr=%p] [len=%lu]\n", addr, len);
>  }
> --
> 2.5.0
>



-- 
Kees Cook
Chrome OS & Brillo Security
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