From 182b967e1119d22889e334c8f1c1b75df41f9165 Mon Sep 17 00:00:00 2001 From: Hans-Frieder Vogt Date: Wed, 3 Oct 2012 05:25:40 -0300 Subject: [PATCH] [media] af9033: prevent unintended underflow 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. [crope@iki.fi: add Reported-by] Reported-by: Dan Carpenter Signed-off-by: Hans-Frieder Vogt Reviewed-by: Antti Palosaari Signed-off-by: Antti Palosaari Signed-off-by: Mauro Carvalho Chehab --- drivers/media/dvb-frontends/af9033.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) diff --git a/drivers/media/dvb-frontends/af9033.c b/drivers/media/dvb-frontends/af9033.c index 8162d939c4b2..464ad878490b 100644 --- a/drivers/media/dvb-frontends/af9033.c +++ b/drivers/media/dvb-frontends/af9033.c @@ -408,7 +408,7 @@ static int af9033_set_frontend(struct dvb_frontend *fe) { 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 dvb_frontend *fe) 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); -- 2.20.1