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From:   Toke =?utf-8?Q?H=C3=B8iland-J=C3=B8rgensen?= <toke@redhat.com>
To:     Dan Carpenter <dan.carpenter@oracle.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()
In-Reply-To: <20191126091150.GA1759@kadam>
References: <20191121213935.2cbgh3qmd4hv4v5a@kili.mountain> <87v9r7ysg0.fsf@toke.dk> <20191126091150.GA1759@kadam>
Date:   Tue, 26 Nov 2019 10:16:10 +0100
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Dan Carpenter <dan.carpenter@oracle.com> writes:

> On Tue, Nov 26, 2019 at 09:04:15AM +0100, Toke H=C3=B8iland-J=C3=B8rgense=
n wrote:
>> Dan Carpenter <dan.carpenter@oracle.com> writes:
>>=20
>> > The sband->bitrates[] array has "sband->n_bitrates" elements so this
>> > check needs to be >=3D instead of > or we could read beyond the end of=
 the
>> > array.
>> >
>> > These values come from when we call mt76_register_device():
>> >
>> > =09ret =3D mt76_register_device(&dev->mt76, true, mt7603_rates,
>> > =09=09=09=09   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/ne=
t/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, str=
uct mt76_rx_status *status,
>> >  =09=09=09return 0;
>> > =20
>> >  =09=09sband =3D dev->hw->wiphy->bands[status->band];
>> > -=09=09if (!sband || status->rate_idx > sband->n_bitrates)
>> > +=09=09if (!sband || status->rate_idx >=3D sband->n_bitrates)
>> >  =09=09=09return 0;
>> > =20
>> >  =09=09rate =3D &sband->bitrates[status->rate_idx];
>>=20
>> 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

Well, it's copy-pasted from the same code ;)

The plan is to get rid of the version inside mt76; was waiting for the
trees to converge, though, so I guess after the merge window?

> I will send a fix for it.

Great, thanks!

-Toke