Subject: Re: [PATCH v2] iwlegacy: 4965: fix possible out-of-bounds access in il4965_tx_cmd_build_rate()

From: Stanislaw Gruszka <[email-masked]>
Date: Tue, 29 Apr 2025 23:40:18 +0200

Hi

On Tue, Apr 29, 2025 at 08:15:59PM +0300, Fedor Pchelkin wrote:
> Hello,
> 
> On Sun, 27. Apr 08:39, Stanislaw Gruszka wrote:
> > > diff --git a/drivers/net/wireless/intel/iwlegacy/4965-mac.c b/drivers/net/wireless/intel/iwlegacy/4965-mac.c
> > > index 78dee8ccfebf..f60d9b9798c1 100644
> > > --- a/drivers/net/wireless/intel/iwlegacy/4965-mac.c
> > > +++ b/drivers/net/wireless/intel/iwlegacy/4965-mac.c
> > > @@ -1572,7 +1572,7 @@ il4965_tx_cmd_build_rate(struct il_priv *il,
> > >  	 */
> > >  	rate_idx = info->control.rates[0].idx;
> > >  	if ((info->control.rates[0].flags & IEEE80211_TX_RC_MCS) || rate_idx < 0
> > > -	    || rate_idx > RATE_COUNT_LEGACY)
> > > +	    || rate_idx >= RATE_COUNT_LEGACY)
> > >  		rate_idx = rate_lowest_index(&il->bands[info->band], sta);
> > 
> > .. so looks the check is fine already and changing it will induce a bug
> > for RATE_54M_INDEX.
> > 
> > Regards
> > Stanislaw
> > 
> > >  	/* For 5 GHZ band, remap mac80211 rate indices into driver indices */
> > >  	if (info->band == NL80211_BAND_5GHZ)
> 
> Here goes the fragment:
> 
> 		rate_idx += IL_FIRST_OFDM_RATE;
> 	/* Get PLCP rate for tx_cmd->rate_n_flags */
> 	rate_plcp = il_rates[rate_idx].plcp;
> 
> > > -- 
> > > 2.39.5 (Apple Git-154)
> > > 
> 
> Looks like the proper checks should be added to address the 5GHZ case and
> validate that the index won't exceed the array boundaries after being shifted
> by IL_FIRST_OFDM_RATE.

Good point. It make sense to move rate_idx range check after possible
IL_FIRST_OFDM_RATE addition for 5GHz.

Regards
Stanislaw