linux-kernel - Re: [PATCH] staging: rtl8712: uninitialized memory in read_bbreg

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Date:   Thu, 21 Mar 2019 09:45:34 +0300
From:   Dan Carpenter <dan.carpenter@...cle.com>
To:     Larry Finger <Larry.Finger@...inger.net>,
        Colin Ian King <colin.king@...onical.com>
Cc:     Florian Schilhabel <florian.c.schilhabel@...glemail.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Michael Straube <straube.linux@...il.com>,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] staging: rtl8712: uninitialized memory in
 read_bbreg_hdl()

On Thu, Mar 21, 2019 at 09:26:38AM +0300, Dan Carpenter wrote:
> Colin King reported a bug in read_bbreg_hdl():
> 
> 	memcpy(pcmd->rsp, (u8 *)&val, pcmd->rspsz);
> 
> The problem is that "val" is uninitialized.
> 
> This code is obviously not useful, but so far as I can tell
> "pcmd->cmdcode" is never GEN_CMD_CODE(_Read_BBREG) so it's not harmful
> either.  For now the easiest fix is to just call r8712_free_cmd_obj()
> and return.
> 
> Fixes: 2865d42c78a9 ("staging: r8712u: Add the new driver to the mainline kernel")
> Reported-by: Colin Ian King <colin.king@...onical.com>
> Signed-off-by: Dan Carpenter <dan.carpenter@...cle.com>
> ---
>  drivers/staging/rtl8712/rtl8712_cmd.c | 10 +---------
>  drivers/staging/rtl8712/rtl8712_cmd.h |  2 +-
>  2 files changed, 2 insertions(+), 10 deletions(-)
> 
> diff --git a/drivers/staging/rtl8712/rtl8712_cmd.h b/drivers/staging/rtl8712/rtl8712_cmd.h
> index 92fb77666d44..1ef86b8c592f 100644
> --- a/drivers/staging/rtl8712/rtl8712_cmd.h
> +++ b/drivers/staging/rtl8712/rtl8712_cmd.h
> @@ -140,7 +140,7 @@ enum rtl8712_h2c_cmd {
>  static struct _cmd_callback	cmd_callback[] = {
>  	{GEN_CMD_CODE(_Read_MACREG), NULL}, /*0*/
>  	{GEN_CMD_CODE(_Write_MACREG), NULL},
> -	{GEN_CMD_CODE(_Read_BBREG), &r8712_getbbrfreg_cmdrsp_callback},
> +	{GEN_CMD_CODE(_Read_BBREG), NULL},
>  	{GEN_CMD_CODE(_Write_BBREG), NULL},
>  	{GEN_CMD_CODE(_Read_RFREG), &r8712_getbbrfreg_cmdrsp_callback},
                                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
>  	{GEN_CMD_CODE(_Write_RFREG), NULL}, /*5*/

The other place that calls r8712_getbbrfreg_cmdrsp_callback() is
read_rfreg_hdl().  For GEN_CMD_CODE(_Read_RFREG) we don't allocate
the ->rsp pointer so we can't kfree() it.  The read_rfreg_hdl()
functions calls r8712_free_cmd_obj() which kfrees it.  But fortunately
that is dead code.

This code is obviously staging code...

It would be fairly straight forward to get rid of the cmd_callback[]
array.

regards,
dan carpenter