linux-kernel - [PATCH][next] ASoC: cx2072x: fix integer overflow on unsigned int multiply

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Message-Id: <20190524222551.26573-1-colin.king@canonical.com>
Date:   Fri, 24 May 2019 23:25:51 +0100
From:   Colin King <colin.king@...onical.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Simon Ho <simon.ho@...exant.com>, alsa-devel@...a-project.org
Cc:     kernel-janitors@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH][next] ASoC: cx2072x: fix integer overflow on unsigned int multiply

From: Colin Ian King <colin.king@...onical.com>

In the case where frac_div larger than 96 the result of an unsigned
multiplication overflows an unsigned int.  For example, this can
happen when the sample_rate is 192000 and pll_input is 122.  Fix
this by casing the first term of the mutiply to a u64. Also remove
the extraneous parentheses around the expression.

Addresses-Coverity: ("Unintentional integer overflow")
Fixes: a497a4363706 ("ASoC: Add support for Conexant CX2072X CODEC")
Signed-off-by: Colin Ian King <colin.king@...onical.com>
---
 sound/soc/codecs/cx2072x.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/codecs/cx2072x.c b/sound/soc/codecs/cx2072x.c
index c11a585bbf70..e8e6fd2e97b6 100644
--- a/sound/soc/codecs/cx2072x.c
+++ b/sound/soc/codecs/cx2072x.c
@@ -627,7 +627,7 @@ static int cx2072x_config_pll(struct cx2072x_priv *cx2072x)
 	if (frac_div) {
 		frac_div *= 1000;
 		frac_div /= pll_input;
-		frac_num = ((4000 + frac_div) * ((1 << 20) - 4));
+		frac_num = (u64)(4000 + frac_div) * ((1 << 20) - 4);
 		do_div(frac_num, 7);
 		frac = ((u32)frac_num + 499) / 1000;
 	}
-- 
2.20.1