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Date:   Wed, 6 Oct 2021 18:13:58 +0200
From:   Michael =?UTF-8?B?QsO8c2No?= <m@bues.ch>
To:     Dan Carpenter <dan.carpenter@oracle.com>
Cc:     Larry Finger <Larry.Finger@lwfinger.net>,
        Kalle Valo <kvalo@codeaurora.org>,
        linux-wireless@vger.kernel.org, b43-dev@lists.infradead.org,
        kernel-janitors@vger.kernel.org
Subject: Re: [PATCH 1/2] b43legacy: fix a lower bounds test
Message-ID: <20211006181358.67a23e18@wiggum>
In-Reply-To: <20211006073542.GD8404@kili>
References: <20211006073542.GD8404@kili>
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On Wed, 6 Oct 2021 10:35:42 +0300
Dan Carpenter <dan.carpenter@oracle.com> wrote:

> The problem is that "channel" is an unsigned int, when it's less 5 the
> value of "channel - 5" is not a negative number as one would expect but
> is very high positive value instead.
>=20
> This means that "start" becomes a very high positive value.  The result
> of that is that we never enter the "for (i =3D start; i <=3D end; i++) {"
> loop.  Instead of storing the result from b43legacy_radio_aci_detect()
> it just uses zero.
>=20
> Fixes: 75388acd0cd8 ("[B43LEGACY]: add mac80211-based driver for legacy B=
CM43xx devices")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>
> ---
> This fix is correct, but making dead code go live can sometimes expose
> bugs which were previously hiding and is always carries a slight risk.
>=20
>  drivers/net/wireless/broadcom/b43legacy/radio.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>=20
> diff --git a/drivers/net/wireless/broadcom/b43legacy/radio.c b/drivers/ne=
t/wireless/broadcom/b43legacy/radio.c
> index 06891b4f837b..fdf78c10a05c 100644
> --- a/drivers/net/wireless/broadcom/b43legacy/radio.c
> +++ b/drivers/net/wireless/broadcom/b43legacy/radio.c
> @@ -283,7 +283,7 @@ u8 b43legacy_radio_aci_scan(struct b43legacy_wldev *d=
ev)
>  			    & 0x7FFF);
>  	b43legacy_set_all_gains(dev, 3, 8, 1);
> =20
> -	start =3D (channel - 5 > 0) ? channel - 5 : 1;
> +	start =3D (channel > 5) ? channel - 5 : 1;
>  	end =3D (channel + 5 < 14) ? channel + 5 : 13;
> =20
>  	for (i =3D start; i <=3D end; i++) {

Nice finding.

Acked-by: Michael B=C3=BCsch <m@bues.ch>


--=20
Michael

https://bues.ch/

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