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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>,
        Felix Fietkau <nbd@nbd.name>
Cc:     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: <20191121213935.2cbgh3qmd4hv4v5a@kili.mountain>
References: <20191121213935.2cbgh3qmd4hv4v5a@kili.mountain>
Date:   Tue, 26 Nov 2019 09:04:15 +0100
Message-ID: <87v9r7ysg0.fsf@toke.dk>
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Dan Carpenter <dan.carpenter@oracle.com> writes:

> 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 th=
e
> 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 sur=
vey")
> 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/w=
ireless/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,
>  =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];

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? :)

-Toke