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

From: <[email-masked]>
Date: Tue, 5 Nov 2019 06:11:03 +0000

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).

> 498     	}
> 499
> 500     	ht_ie = cfg80211_find_ie(WLAN_EID_HT_CAPABILITY, ies->data, ies->len);
> 501     	if (ht_ie)
> 
> If this is a false positive, please let us know so we can mark it as
> such, or teach the Coverity rules to be smarter. If not, please make
> sure fixes get into linux-next. :) For patches fixing this, please
> include these lines (but double-check the "Fixes" first):
> 
> Reported-by: coverity-bot <[email-masked]>
> Addresses-Coverity-ID: 1487400 ("Memory - illegal accesses")
> Fixes: 4e0b0f42c9c7 ("staging: wilc1000: use struct to pack join parameters for FW")
> 
> 
> Thanks for your attention!
>