FAILED: patch "[PATCH] ASoC: rt5682: fix an incorrect NULL check on list iterator" failed to apply to 5.15-stable tree

The patch below does not apply to the 5.15-stable tree.
If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to <[email protected]>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From c8618d65007ba68d7891130642d73e89372101e8 Mon Sep 17 00:00:00 2001
From: Xiaomeng Tong <[email protected]>
Date: Sun, 27 Mar 2022 16:10:02 +0800
Subject: [PATCH] ASoC: rt5682: fix an incorrect NULL check on list iterator

The bug is here:

	if (!dai) {

The list iterator value 'dai' will *always* be set and non-NULL by for_each_component_dais(), so it is incorrect to assume that the iterator value will be NULL if the list is empty or no element is found (In fact, it will be a bogus pointer to an invalid struct object containing the HEAD). Otherwise it will bypass the check 'if (!dai) {' (never call dev_err() and never return -ENODEV;) and lead to invalid memory access lately when calling 'rt5682_set_bclk1_ratio(dai, factor);'.

To fix the bug, just return rt5682_set_bclk1_ratio(dai, factor); when found the 'dai', otherwise dev_err() and return -ENODEV;

index be68d573a490..c9ff9c89adf7 100644
@@ -2822,14 +2822,11 @@ static int rt5682_bclk_set_rate(struct clk_hw *hw, unsigned long rate,
 
 	for_each_component_dais(component, dai)
 		if (dai->id == RT5682_AIF1)
-			break;
-	if (!dai) {
-		dev_err(rt5682->i2c_dev, "dai %d not found in component\n",
-			RT5682_AIF1);
-		return -ENODEV;
-	}
+			return rt5682_set_bclk1_ratio(dai, factor);
 
-	return rt5682_set_bclk1_ratio(dai, factor);
+	dev_err(rt5682->i2c_dev, "dai %d not found in component\n",
+		RT5682_AIF1);
+	return -ENODEV;
 }
 
 static const struct clk_ops rt5682_dai_clk_ops[RT5682_DAI_NUM_CLKS] = {