linux-kernel - Re: [PATCH] Staging: comedi: fix information leak

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Date:	Mon, 09 Mar 2015 23:34:42 +0000
From:	Ian Abbott <abbotti@....co.uk>
To:	Matteo Semenzato <mattew8898@...il.com>,
	gregkh@...uxfoundation.org, hsweeten@...ionengravers.com
CC:	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Staging: comedi: fix information leak

On 09/03/15 20:08, Matteo Semenzato wrote:
> From: Matteo Semenzato <mattew8898@...il.com>
>
> The comedi_cmd struct has an hole after chanlist_len that could contain uninitialized
> memory, this struct is copied to userspace.
>
> Signed-off-by: Matteo Semenato <mattew8898@...il.com>
> ---
>   drivers/staging/comedi/comedi_fops.c | 2 ++
>   1 file changed, 2 insertions(+)
>
> diff --git a/drivers/staging/comedi/comedi_fops.c b/drivers/staging/comedi/comedi_fops.c
> index 727640e..1cdf0a2 100644
> --- a/drivers/staging/comedi/comedi_fops.c
> +++ b/drivers/staging/comedi/comedi_fops.c
> @@ -1718,6 +1718,8 @@ static int do_cmdtest_ioctl(struct comedi_device *dev,
>   	unsigned int __user *user_chanlist;
>   	int ret;
>
> +	memset(&cmd, 0, sizeof(cmd));
> +
>   	/* get the user's cmd and do some simple validation */
>   	ret = __comedi_get_user_cmd(dev, arg, &cmd);
>   	if (ret)
>

I see no information leak there.  The cmd variable gets copied over with 
user memory by the call to __comedi_get_user_cmd(), so zero-filling it 
first is rather pointless.

-- 
-=( Ian Abbott @ MEV Ltd.    E-mail: <abbotti@....co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-
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