linux-kernel - Re: [PATCH v7u1 14/31] x86, boot: move checking of cmd_line

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Message-ID: <20130107160042.GG29449@x1.alien8.de>
Date:	Mon, 7 Jan 2013 17:00:42 +0100
From:	Borislav Petkov <bp@...en8.de>
To:	Yinghai Lu <yinghai@...nel.org>
Cc:	Thomas Gleixner <tglx@...utronix.de>, Ingo Molnar <mingo@...e.hu>,
	"H. Peter Anvin" <hpa@...or.com>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jan Kiszka <jan.kiszka@....de>,
	Jason Wessel <jason.wessel@...driver.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7u1 14/31] x86, boot: move checking of cmd_line_ptr out
 of common path

On Thu, Jan 03, 2013 at 04:48:34PM -0800, Yinghai Lu wrote:
> cmdline.c::__cmdline_find_option... are shared between 16-bit setup code
> and 32/64 bit decompressor code.
> 
> for 32/64 only path via kexec, we should not check if ptr is less 1M.
> as those cmdline could be put above 1M, or even 4G.
> 
> Move out accessible checking out of __cmdline_find_option()
> So decompressor in misc.c can parse cmdline correctly.
> 
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> ---
>  arch/x86/boot/boot.h    |   14 ++++++++++++--
>  arch/x86/boot/cmdline.c |    8 ++++----
>  2 files changed, 16 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/x86/boot/boot.h b/arch/x86/boot/boot.h
> index 18997e5..7fadf80 100644
> --- a/arch/x86/boot/boot.h
> +++ b/arch/x86/boot/boot.h
> @@ -289,12 +289,22 @@ int __cmdline_find_option(u32 cmdline_ptr, const char *option, char *buffer, int
>  int __cmdline_find_option_bool(u32 cmdline_ptr, const char *option);
>  static inline int cmdline_find_option(const char *option, char *buffer, int bufsize)
>  {
> -	return __cmdline_find_option(boot_params.hdr.cmd_line_ptr, option, buffer, bufsize);
> +	u32 cmd_line_ptr = boot_params.hdr.cmd_line_ptr;

This check could very well use a comment for why we're checking it to be
under 1Mb, no matter that the original code didn't have it.

> +	if (cmd_line_ptr >= 0x100000)
> +		return -1;      /* inaccessible */
> +
> +	return __cmdline_find_option(cmd_line_ptr, option, buffer, bufsize);
>  }

[ … ]

Thanks.

-- 
Regards/Gruss,
Boris.
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