linux-kernel - [PATCH] ASoC: nau8810: use 64-bit arithmetic instead of 32-bit

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Message-ID: <20180705151407.GA30984@embeddedor.com>
Date:   Thu, 5 Jul 2018 10:14:07 -0500
From:   "Gustavo A. R. Silva" <gustavo@...eddedor.com>
To:     Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        "Gustavo A. R. Silva" <gustavo@...eddedor.com>
Subject: [PATCH] ASoC: nau8810: use 64-bit arithmetic instead of 32-bit

Add suffix ULL to constant 256 in order to give the compiler complete
information about the proper arithmetic to use.

Notice that such constant is used in a context that expects an
expression of type u64 (64 bits, unsigned) and the following
expression is currently being evaluated using 32-bit arithmetic:

256 * fs * 4 * nau8810_mclk_scaler[i] / 10

Addresses-Coverity-ID: 1357595 ("Unintentional integer overflow")
Signed-off-by: Gustavo A. R. Silva <gustavo@...eddedor.com>
---
 sound/soc/codecs/nau8810.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/codecs/nau8810.c b/sound/soc/codecs/nau8810.c
index bfd74b8..e7fd0b2 100644
--- a/sound/soc/codecs/nau8810.c
+++ b/sound/soc/codecs/nau8810.c
@@ -505,7 +505,7 @@ static int nau88l0_calc_pll(unsigned int pll_in,
 	f2_max = 0;
 	scal_sel = ARRAY_SIZE(nau8810_mclk_scaler);
 	for (i = 0; i < ARRAY_SIZE(nau8810_mclk_scaler); i++) {
-		f2 = 256 * fs * 4 * nau8810_mclk_scaler[i] / 10;
+		f2 = 256ULL * fs * 4 * nau8810_mclk_scaler[i] / 10;
 		if (f2 > NAU_PLL_FREQ_MIN && f2 < NAU_PLL_FREQ_MAX &&
 			f2_max < f2) {
 			f2_max = f2;
-- 
2.7.4