Subject: Re: [PATCH] mwl8k: Avoid memcpy() over-reading of ETH_SS_STATS

From: Kees Cook <[email-masked]>
Date: Wed, 16 Jun 2021 20:22:52 -0700

On Wed, Jun 16, 2021 at 09:58:09PM +0200, Andrew Lunn wrote:
> On Wed, Jun 16, 2021 at 12:52:42PM -0700, Kees Cook wrote:
> > In preparation for FORTIFY_SOURCE performing compile-time and run-time
> > field bounds checking for memcpy(), memmove(), and memset(), avoid
> > intentionally reading across neighboring array fields. Use the
> > sub-structure address directly.
> > 
> > Signed-off-by: Kees Cook <[email-masked]>
> > ---
> >  drivers/net/wireless/marvell/mwl8k.c | 4 ++--
> >  1 file changed, 2 insertions(+), 2 deletions(-)
> > 
> > diff --git a/drivers/net/wireless/marvell/mwl8k.c b/drivers/net/wireless/marvell/mwl8k.c
> > index 84b32a5f01ee..3bf6571f4149 100644
> > --- a/drivers/net/wireless/marvell/mwl8k.c
> > +++ b/drivers/net/wireless/marvell/mwl8k.c
> > @@ -4552,7 +4552,7 @@ static int mwl8k_cmd_update_stadb_add(struct ieee80211_hw *hw,
> >  	else
> >  		rates = sta->supp_rates[NL80211_BAND_5GHZ] << 5;
> >  	legacy_rate_mask_to_array(p->legacy_rates, rates);
> > -	memcpy(p->ht_rates, sta->ht_cap.mcs.rx_mask, 16);
> > +	memcpy(p->ht_rates, &sta->ht_cap.mcs, 16);
> >  	p->interop = 1;
> >  	p->amsdu_enabled = 0;
> >  
> > @@ -5034,7 +5034,7 @@ mwl8k_bss_info_changed_sta(struct ieee80211_hw *hw, struct ieee80211_vif *vif,
> >  			ap_legacy_rates =
> >  				ap->supp_rates[NL80211_BAND_5GHZ] << 5;
> >  		}
> > -		memcpy(ap_mcs_rates, ap->ht_cap.mcs.rx_mask, 16);
> > +		memcpy(ap_mcs_rates, &ap->ht_cap.mcs, 16);
> >  
> >  		rcu_read_unlock();
> 
> This does not appear to have anything to do with ETH_SS_STATS which is
> what the Subject: says.

Whoops! I was off-by-one in my Subject edits. I will respin.

-Kees

-- 
Kees Cook