linux-kernel - Re: [PATCH 6/8] char: synclink: fix information leak to userland

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Message-ID: <4CBB3667.2010804@suse.cz>
Date:	Sun, 17 Oct 2010 19:46:15 +0200
From:	Jiri Slaby <jslaby@...e.cz>
To:	Vasiliy Kulikov <segooon@...il.com>
CC:	kernel-janitors@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...e.de>,
	Alan Cox <alan@...ux.intel.com>, Arnd Bergmann <arnd@...db.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/8] char: synclink: fix information leak to userland

On 10/17/2010 05:38 PM, Vasiliy Kulikov wrote:
> On Sun, Oct 17, 2010 at 17:34 +0200, Jiri Slaby wrote:
>> On 10/17/2010 04:41 PM, Vasiliy Kulikov wrote:
>>> Structure new_line is copied to userland with some padding fields unitialized.
>>> It leads to leaking of stack memory.
>>
>> I think your tool has a bug. I must admit I fail to see the padding
>> which would cause leaks. Could you elaborate?
> 
> I didn't use any tool except "grep copy_to_user" :)
> 
>     typedef struct { 
>         unsigned int clock_rate; /* bits per second */
>         unsigned int clock_type; /* internal, external, TX-internal etc. */
>         unsigned short loopback;
>     } sync_serial_settings;          /* V.35, V.24, X.21 */
> 
> On x86_64 sizeof(sync_serial_settings) = 4 + 4 + 2 + 2 = 12.
> The last 2 is padding.

Ah, good to know that even end of structures is padded.

thanks for clarification,
-- 
js
suse labs
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