linux-kernel - Re: [PATCH 6/6] staging: pi433: Rename enum modShaping in rf69

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Date:   Mon, 4 Dec 2017 20:59:35 +0200
From:   Marcus Wolf <marcus.wolf@...rthome-wolf.de>
To:     Dan Carpenter <dan.carpenter@...cle.com>,
        Simon Sandström <simon@...anor.nu>
Cc:     gregkh@...uxfoundation.org, devel@...verdev.osuosl.org,
        linux@...f-Entwicklungen.de, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 6/6] staging: pi433: Rename enum modShaping in rf69_enum.h


Am 04.12.2017 um 12:33 schrieb Dan Carpenter:
> On Sun, Dec 03, 2017 at 04:17:26PM +0100, Simon Sandström wrote:
>> diff --git a/drivers/staging/pi433/pi433_if.h b/drivers/staging/pi433/pi433_if.h
>> index 34ff0d4807bd..bcfe29840889 100644
>> --- a/drivers/staging/pi433/pi433_if.h
>> +++ b/drivers/staging/pi433/pi433_if.h
>> @@ -63,7 +63,7 @@ struct pi433_tx_cfg {
>>   	__u16			bit_rate;
>>   	__u32			dev_frequency;
>>   	enum modulation		modulation;
>> -	enum modShaping		modShaping;
>> +	enum mod_shaping	mod_shaping;
>>   
> 
> I looked at how mod_shaping is set and the only place is in the ioctl:
> 
>     789          case PI433_IOC_WR_TX_CFG:
>     790                  if (copy_from_user(&instance->tx_cfg, argp,
>     791                                          sizeof(struct pi433_tx_cfg)))
>     792                          return -EFAULT;
>     793                  break;
> 
> We just write over the whole config.  Including important things like
> rx_cfg.fixed_message_length.  There is no locking so when we do things
> like:
> 
>     385          /* fixed or unlimited length? */
>     386          if (dev->rx_cfg.fixed_message_length != 0)
>     387          {
>     388                  if (dev->rx_cfg.fixed_message_length > dev->rx_buffer_size)
>                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> check
> 
>     389                  {
>     390                          retval = -1;
>     391                          goto abort;
>     392                  }
>     393                  bytes_total = dev->rx_cfg.fixed_message_length;
>                                        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
> set this in the ioctl after the check but before this line and it looks
> like a security problem.
> 
>     394                  dev_dbg(dev->dev,"rx: msg len set to %d by fixed length", bytes_total);
>     395          }
> 
> Anyway, I guess this patch is fine.
> 
> regards,
> dan carpenter
> 

Hi Dan,

you are mixing rx and tx. The part from IOCTL is copied from the 
tx-part, the lower part is dealing with rx.

With rx there should be no problem, since IOCTL is blocked, as long as 
an rx operation is going on.

With tx, I also expect no problems, since instance->tx_cfg is never used 
to configure the rf69. Everytime, you pass in new data via write() a 
copy of tx_cfg is made. Transmission is done, using the copy of the 
tx_cfg, never by using instance->tx_cfg.

But maybe I didn't got your point and misunderstand your intention.

Cheers,

Marcus