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Date:   Tue, 26 Nov 2019 12:11:50 +0300
From:   Dan Carpenter <dan.carpenter@oracle.com>
To:     Toke =?iso-8859-1?Q?H=F8iland-J=F8rgensen?= <toke@redhat.com>
Cc:     Felix Fietkau <nbd@nbd.name>,
        Lorenzo Bianconi <lorenzo.bianconi83@gmail.com>,
        Ryder Lee <ryder.lee@mediatek.com>,
        Roy Luo <royluo@google.com>, Kalle Valo <kvalo@codeaurora.org>,
        Matthias Brugger <matthias.bgg@gmail.com>,
        linux-wireless@vger.kernel.org, linux-mediatek@lists.infradead.org,
        kernel-janitors@vger.kernel.org
Subject: Re: [PATCH] mt76: Off by one in mt76_calc_rx_airtime()
Message-ID: <20191126091150.GA1759@kadam>
References: <20191121213935.2cbgh3qmd4hv4v5a@kili.mountain>
 <87v9r7ysg0.fsf@toke.dk>
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On Tue, Nov 26, 2019 at 09:04:15AM +0100, Toke H?iland-J?rgensen wrote:
> Dan Carpenter <dan.carpenter@oracle.com> writes:
> 
> > The sband->bitrates[] array has "sband->n_bitrates" elements so this
> > check needs to be >= instead of > or we could read beyond the end of the
> > array.
> >
> > These values come from when we call mt76_register_device():
> >
> > 	ret = mt76_register_device(&dev->mt76, true, mt7603_rates,
> > 				   ARRAY_SIZE(mt7603_rates));
> >
> > Here sband->bitrates[] is mt7603_rates[] and ->n_bitrates is the
> > ARRAY_SIZE()
> >
> > Fixes: 5ce09c1a7907 ("mt76: track rx airtime for airtime fairness and survey")
> > Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> > ---
> >  drivers/net/wireless/mediatek/mt76/airtime.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/wireless/mediatek/mt76/airtime.c b/drivers/net/wireless/mediatek/mt76/airtime.c
> > index 55116f395f9a..a4a785467748 100644
> > --- a/drivers/net/wireless/mediatek/mt76/airtime.c
> > +++ b/drivers/net/wireless/mediatek/mt76/airtime.c
> > @@ -242,7 +242,7 @@ u32 mt76_calc_rx_airtime(struct mt76_dev *dev, struct mt76_rx_status *status,
> >  			return 0;
> >  
> >  		sband = dev->hw->wiphy->bands[status->band];
> > -		if (!sband || status->rate_idx > sband->n_bitrates)
> > +		if (!sband || status->rate_idx >= sband->n_bitrates)
> >  			return 0;
> >  
> >  		rate = &sband->bitrates[status->rate_idx];
> 
> This code has recently been ported to mac80211 (net/mac80211/airtime.c).
> It seems that the bug is also present there; care to send a patch for
> that as well? :)

Oh.  Thanks for pointing that out.  I actually saw the static checker
warning for that and ignored it thinking that it was the same code.  :P

I will send a fix for it.

regards,
dan carpenter