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

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Date:	Sun, 17 Oct 2010 19:36:09 +0200
From:	Dan Carpenter <error27@...il.com>
To:	Vasiliy Kulikov <segooon@...il.com>
Cc:	Jiri Slaby <jslaby@...e.cz>, 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 Sun, Oct 17, 2010 at 07:38:39PM +0400, 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" :)
> 

It seems like you should be able to use pahole to make a list of
structs with padding and then a checker script to find places where
information is leaked.

Also someone complained to me about when I added a memset() in a fast
path.  The thought was that it might be faster to just initialize it
instead like:

	struct foo bar = {};

In my case just using the initializer made the code cleaner so I did it,
but neither of us actually benchmarked it.

regards,
dan carpenter
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