linux-kernel - Re: [PATCH] x86/mm/ptdump: Make (debugfs)/kernel_page

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Message-ID: <CAGXu5jJhNJwvgkEyHYo0UzKL7gVTjHLufDhpM+dBAqEdOVz=BQ@mail.gmail.com>
Date:	Fri, 4 Dec 2015 05:57:05 -0800
From:	Kees Cook <keescook@...omium.org>
To:	Borislav Petkov <bp@...en8.de>
Cc:	X86 ML <x86@...nel.org>, LKML <linux-kernel@...r.kernel.org>,
	Arjan van de Ven <arjan@...ux.intel.com>
Subject: Re: [PATCH] x86/mm/ptdump: Make (debugfs)/kernel_page_tables read-only

On Mon, Nov 30, 2015 at 4:12 AM, Borislav Petkov <bp@...en8.de> wrote:
> From: Borislav Petkov <bp@...e.de>
>
> File should be created with S_IRUSR and not with S_IWUSR too because
> writing to it doesn't make any sense. I mean, we don't have a ->write
> method anyway but let's have the permissions correct too.
>
> Signed-off-by: Borislav Petkov <bp@...e.de>
> Cc: Arjan van de Ven <arjan@...ux.intel.com>

We need a EHAHANOPE errno and have write return that. ;)

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

-Kees

> ---
>  arch/x86/mm/debug_pagetables.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/arch/x86/mm/debug_pagetables.c b/arch/x86/mm/debug_pagetables.c
> index b35ee86a9316..bfcffdf6c577 100644
> --- a/arch/x86/mm/debug_pagetables.c
> +++ b/arch/x86/mm/debug_pagetables.c
> @@ -26,7 +26,7 @@ static struct dentry *pe;
>
>  static int __init pt_dump_debug_init(void)
>  {
> -       pe = debugfs_create_file("kernel_page_tables", 0600, NULL, NULL,
> +       pe = debugfs_create_file("kernel_page_tables", S_IRUSR, NULL, NULL,
>                                  &ptdump_fops);
>         if (!pe)
>                 return -ENOMEM;
> --
> 2.3.5
>
> --
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-- 
Kees Cook
Chrome OS & Brillo Security
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