From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail.kapsi.fi ([217.30.184.167]:34925 "EHLO mail.kapsi.fi" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751845Ab2JCJcV (ORCPT ); Wed, 3 Oct 2012 05:32:21 -0400 Message-ID: <506C060D.1020600@iki.fi> Date: Wed, 03 Oct 2012 12:31:57 +0300 From: Antti Palosaari MIME-Version: 1.0 To: Hans-Frieder Vogt CC: Dan Carpenter , linux-media@vger.kernel.org Subject: Re: [PATCH] af9033: prevent unintended underflow References: <201210031125.40850.hfvogt@gmx.net> In-Reply-To: <201210031125.40850.hfvogt@gmx.net> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-media-owner@vger.kernel.org List-ID: On 10/03/2012 12:25 PM, Hans-Frieder Vogt wrote: > As spotted by Dan Carpenter (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 Acked-by: Antti Palosaari 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 gmx .dot. net > -- > To unsubscribe from this list: send the line "unsubscribe linux-media" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > -- http://palosaari.fi/