From: Antti Palosaari <crope@iki.fi>
To: Hans-Frieder Vogt <hfvogt@gmx.net>
Cc: Dan Carpenter <dan.carpenter@oracle.com>, linux-media@vger.kernel.org
Subject: Re: [PATCH] af9033: prevent unintended underflow
Date: Wed, 03 Oct 2012 12:31:57 +0300 [thread overview]
Message-ID: <506C060D.1020600@iki.fi> (raw)
In-Reply-To: <201210031125.40850.hfvogt@gmx.net>
On 10/03/2012 12:25 PM, Hans-Frieder Vogt wrote:
> As spotted by Dan Carpenter <dan.carpenter@oracle.com> (thanks!), we have
> improperly used an unsigned variable in a calculation that may result in a
> negative number. This may cause an unintended underflow if the interface
> frequency of the tuner is > approx. 40MHz.
> This patch should resolve the issue, following an approach similar to what is
> used in af9013.c.
>
> Signed-off-by: Hans-Frieder Vogt <hfvogt@gmx.net>
Acked-by: Antti Palosaari <crope@iki.fi>
I will PULL-request that via my tree for 3.7. I don't see any reason
this should go older ones.
regards
Antti
>
> drivers/media/dvb-frontends/af9033.c | 16 +++++++++-------
> 1 file changed, 9 insertions(+), 7 deletions(-)
>
> --- a/drivers/media/dvb-frontends/af9033.c 2012-09-28 05:45:17.000000000 +0200
> +++ b/drivers/media/dvb-frontends/af9033.c 2012-10-03 11:08:18.160894181 +0200
> @@ -408,7 +408,7 @@ static int af9033_set_frontend(struct dv
> {
> struct af9033_state *state = fe->demodulator_priv;
> struct dtv_frontend_properties *c = &fe->dtv_property_cache;
> - int ret, i, spec_inv;
> + int ret, i, spec_inv, sampling_freq;
> u8 tmp, buf[3], bandwidth_reg_val;
> u32 if_frequency, freq_cw, adc_freq;
>
> @@ -465,18 +465,20 @@ static int af9033_set_frontend(struct dv
> else
> if_frequency = 0;
>
> - while (if_frequency > (adc_freq / 2))
> - if_frequency -= adc_freq;
> + sampling_freq = if_frequency;
>
> - if (if_frequency >= 0)
> + while (sampling_freq > (adc_freq / 2))
> + sampling_freq -= adc_freq;
> +
> + if (sampling_freq >= 0)
> spec_inv *= -1;
> else
> - if_frequency *= -1;
> + sampling_freq *= -1;
>
> - freq_cw = af9033_div(state, if_frequency, adc_freq, 23ul);
> + freq_cw = af9033_div(state, sampling_freq, adc_freq, 23ul);
>
> if (spec_inv == -1)
> - freq_cw *= -1;
> + freq_cw = 0x800000 - freq_cw;
>
> /* get adc multiplies */
> ret = af9033_rd_reg(state, 0x800045, &tmp);
>
> Hans-Frieder Vogt e-mail: hfvogt <at> gmx .dot. net
> --
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>
--
http://palosaari.fi/
prev parent reply other threads:[~2012-10-03 9:32 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-03 9:25 [PATCH] af9033: prevent unintended underflow Hans-Frieder Vogt
2012-10-03 9:31 ` Antti Palosaari [this message]
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