linux-kernel - [PATCH] ALSA: rockchip: fix a possible divide-by-zero bug in rockchip_i2s_hw

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Message-Id: <20200830095106.4412-1-t-li20@mails.tsinghua.edu.cn>
Date:   Sun, 30 Aug 2020 17:51:06 +0800
From:   Tuo Li <t-li20@...ls.tsinghua.edu.cn>
To:     lgirdwood@...il.com, broonie@...nel.org, perex@...ex.cz,
        tiwai@...e.com, heiko@...ech.de, baijiaju1990@...il.com
Cc:     alsa-devel@...a-project.org, linux-arm-kernel@...ts.infradead.org,
        linux-rockchip@...ts.infradead.org, linux-kernel@...r.kernel.org,
        Tuo Li <t-li20@...ls.tsinghua.edu.cn>
Subject: [PATCH] ALSA: rockchip: fix a possible divide-by-zero bug in rockchip_i2s_hw_params()

The variable bclk_rate is checked in:
  if (bclk_rate && mclk_rate % bclk_rate)

This indicates that bclk_rate can be zero.
If so, a divide-by-zero bug will occur:
  div_bclk = mclk_rate / bclk_rate;

To fix this possible bug, the function returns -EINVAL when bclk_rate is
zero.

Signed-off-by: Tuo Li <t-li20@...ls.tsinghua.edu.cn>
---
 sound/soc/rockchip/rockchip_i2s.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/soc/rockchip/rockchip_i2s.c b/sound/soc/rockchip/rockchip_i2s.c
index d1438753edb4..dd0836c32639 100644
--- a/sound/soc/rockchip/rockchip_i2s.c
+++ b/sound/soc/rockchip/rockchip_i2s.c
@@ -279,7 +279,9 @@ static int rockchip_i2s_hw_params(struct snd_pcm_substream *substream,
 	if (i2s->is_master_mode) {
 		mclk_rate = clk_get_rate(i2s->mclk);
 		bclk_rate = 2 * 32 * params_rate(params);
-		if (bclk_rate && mclk_rate % bclk_rate)
+		if (bclk_rate == 0)
+			return -EINVAL;
+		if (mclk_rate % bclk_rate)
 			return -EINVAL;
 
 		div_bclk = mclk_rate / bclk_rate;
-- 
2.17.1