Re: Coverity: wilc_parse_join_bss_param(): Memory - illegal accesses

[<Ajay.Kathat@microchip.com>]

On 05-Nov-19 10:42 PM, Kees Cook wrote:
> External E-Mail
> 
> 
> On Tue, Nov 05, 2019 at 06:11:03AM +0000, Ajay.Kathat@microchip.com wrote:
>>
>>
>> On 04-Nov-19 11:08 PM, coverity-bot wrote:
>>> External E-Mail
>>>
>>>
>>> Hello!
>>>
>>> This is an experimental automated report about issues detected by Coverity
>>> from a scan of next-20191031 as part of the linux-next weekly scan project:
>>> https://scan.coverity.com/projects/linux-next-weekly-scan
>>>
>>> You're getting this email because you were associated with the identified
>>> lines of code (noted below) that were touched by recent commits:
>>>
>>> 4e0b0f42c9c7 ("staging: wilc1000: use struct to pack join parameters for FW")
>>>
>>> Coverity reported the following:
>>>
>>> *** CID 1487400:  Memory - illegal accesses  (OVERRUN)
>>> /drivers/staging/wilc1000/wilc_hif.c: 496 in wilc_parse_join_bss_param()
>>> 490     	if (supp_rates_ie) {
>>> 491     		if (supp_rates_ie[1] > (WILC_MAX_RATES_SUPPORTED - rates_len))
>>> 492     			param->supp_rates[0] = WILC_MAX_RATES_SUPPORTED;
>>> 493     		else
>>> 494     			param->supp_rates[0] += supp_rates_ie[1];
>>> 495
>>> vvv     CID 1487400:  Memory - illegal accesses  (OVERRUN)
>>> vvv     Overrunning array of 13 bytes at byte offset 13 by dereferencing pointer "&param->supp_rates[rates_len + 1]". [Note: The source code implementation of the function has been overridden by a builtin model.]
>>> 496     		memcpy(&param->supp_rates[rates_len + 1], supp_rates_ie + 2,
>>> 497     		       (param->supp_rates[0] - rates_len));
>>
>> As I understand, Ideally this condition should never arise because the
>> maximum number of supported *basic rates* is up to 8 so the value of
>> ‘rate_len’ will always be less then WILC_MAX_RATES_SUPPPRTED (i.e 12).
>> Therefore '&param->supp_rates[rates_len+ 1]' will never try to access
>> the 13 bytes in the array.
>> But for the safer side, if need I can create a patch to block the
>> addition of extended supported rates in ‘param->supp_rates’ array if
>> ‘rates_len’ is 12 (i.e 'param->supp_rates' array is full after filing
>> the basic supported rates).
> 
> I don't know the code myself, but generally speaking, it's best to
> validate any assumptions like this. I'd say add a patch for it, since it
> sounds pretty straight-forward to test.

Sure, I will add a patch for this.

Regards,
Ajay