ASoC: codecs: Fix atomicity violation in snd_soc_component_get_drvdata()

An atomicity violation occurs when the validity of the variables
da7219->clk_src and da7219->mclk_rate is being assessed. Since the entire
assessment is not protected by a lock, the da7219 variable might still be
in flux during the assessment, rendering this check invalid.

To fix this issue, we recommend adding a lock before the block
if ((da7219->clk_src == clk_id) && (da7219->mclk_rate == freq)) so that
the legitimacy check for da7219->clk_src and da7219->mclk_rate is
protected by the lock, ensuring the validity of the check.

This possible bug is found by an experimental static analysis tool
developed by our team. This tool analyzes the locking APIs
to extract function pairs that can be concurrently executed, and then
analyzes the instructions in the paired functions to identify possible
concurrency bugs including data races and atomicity violations.

Fixes: 6d817c0 ("ASoC: codecs: Add da7219 codec driver")
Cc: [email protected]
Signed-off-by: Qiu-ji Chen <[email protected]>
Link: https://patch.msgid.link/[email protected]
Signed-off-by: Mark Brown <[email protected]>

Author: TomRita999

sound/soc/codecs/da7219.c

@@ -1167,17 +1167,20 @@ static int da7219_set_dai_sysclk(struct snd_soc_dai *codec_dai,
 	struct da7219_priv *da7219 = snd_soc_component_get_drvdata(component);
 	int ret = 0;
 
-	if ((da7219->clk_src == clk_id) && (da7219->mclk_rate == freq))
+	mutex_lock(&da7219->pll_lock);
+
+	if ((da7219->clk_src == clk_id) && (da7219->mclk_rate == freq)) {
+		mutex_unlock(&da7219->pll_lock);
 		return 0;
+	}
 
 	if ((freq < 2000000) || (freq > 54000000)) {
+		mutex_unlock(&da7219->pll_lock);
 		dev_err(codec_dai->dev, "Unsupported MCLK value %d\n",
 			freq);
 		return -EINVAL;
 	}
 
-	mutex_lock(&da7219->pll_lock);
-
 	switch (clk_id) {
 	case DA7219_CLKSRC_MCLK_SQR:
 		snd_soc_component_update_bits(component, DA7219_PLL_CTRL,