[PATCH] Staging: comedi: fix information leak

[PATCH] Staging: comedi: fix information leak

[Matteo Semenzato]

From: Matteo Semenzato <mattew8898@gmail.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@gmail.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)
-- 
2.3.2

Re: [PATCH] Staging: comedi: fix information leak

[Ian Abbott]

On 09/03/15 20:08, Matteo Semenzato wrote:
> From: Matteo Semenzato <mattew8898@gmail.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@gmail.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@mev.co.uk> )=-
-=(                          Web: http://www.mev.co.uk/  )=-

Re: [PATCH] Staging: comedi: fix information leak

[Dan Carpenter]

On Mon, Mar 09, 2015 at 09:08:17PM +0100, Matteo Semenzato wrote:
> From: Matteo Semenzato <mattew8898@gmail.com>
> 
> The comedi_cmd struct has an hole after chanlist_len that could contain uninitialized
> memory, this struct is copied to userspace.
> 

Is this a Smatch warning?  If so then, I appologize because it's a false
positive.  You really need to have the cross function database built for
that test to work.

The struct is initialized in __comedi_get_user_cmd().

regards,
dan carpenter