linux-kernel - [PATCH 1/3] ASoC: Intel: catpt: remove check of list iterator against head past the loop body

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Date:   Thu, 31 Mar 2022 23:50:01 +0200
From:   Jakob Koschel <jakobkoschel@...il.com>
To:     Codrin Ciubotariu <codrin.ciubotariu@...rochip.com>
Cc:     Arnd Bergmann <arnd@...db.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Nicolas Ferre <nicolas.ferre@...rochip.com>,
        Alexandre Belloni <alexandre.belloni@...tlin.com>,
        Claudiu Beznea <claudiu.beznea@...rochip.com>,
        Cezary Rojewski <cezary.rojewski@...el.com>,
        Pierre-Louis Bossart <pierre-louis.bossart@...ux.intel.com>,
        Liam Girdwood <liam.r.girdwood@...ux.intel.com>,
        Jie Yang <yang.jie@...ux.intel.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>,
        Takashi Iwai <tiwai@...e.com>,
        Orson Zhai <orsonzhai@...il.com>,
        Baolin Wang <baolin.wang7@...il.com>,
        Chunyan Zhang <zhang.lyra@...il.com>,
        Yang Yingliang <yangyingliang@...wei.com>,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
        alsa-devel@...a-project.org, Mike Rapoport <rppt@...nel.org>,
        "Brian Johannesmeyer" <bjohannesmeyer@...il.com>,
        Cristiano Giuffrida <c.giuffrida@...nl>,
        "Bos, H.J." <h.j.bos@...nl>, Jakob Koschel <jakobkoschel@...il.com>
Subject: [PATCH 1/3] ASoC: Intel: catpt: remove check of list iterator against head past the loop body

When list_for_each_entry() completes the iteration over the whole list
without breaking the loop, the iterator value will be a bogus pointer
computed based on the head element.

While it is safe to use the pointer to determine if it was computed
based on the head element, either with list_entry_is_head() or
&pos->member == head, using the iterator variable after the loop should
be avoided.

In preparation to limiting the scope of a list iterator to the list
traversal loop, use a dedicated pointer to point to the found element [1].

Link: https://lore.kernel.org/all/CAHk-=wgRr_D8CB-D9Kg-c=EHreAsk5SqXPwr9Y7k9sA6cWXJ6w@mail.gmail.com/ [1]
Signed-off-by: Jakob Koschel <jakobkoschel@...il.com>
---
 sound/soc/intel/catpt/pcm.c | 13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/sound/soc/intel/catpt/pcm.c b/sound/soc/intel/catpt/pcm.c
index a26000cd5ceb..b103b2d4026e 100644
--- a/sound/soc/intel/catpt/pcm.c
+++ b/sound/soc/intel/catpt/pcm.c
@@ -330,7 +330,8 @@ static int catpt_dai_apply_usettings(struct snd_soc_dai *dai,
 				     struct catpt_stream_runtime *stream)
 {
 	struct snd_soc_component *component = dai->component;
-	struct snd_kcontrol *pos;
+	struct snd_kcontrol *pos = NULL;
+	struct snd_kcontrol *iter;
 	struct catpt_dev *cdev = dev_get_drvdata(dai->dev);
 	const char *name;
 	int ret;
@@ -354,12 +355,14 @@ static int catpt_dai_apply_usettings(struct snd_soc_dai *dai,
 		return 0;
 	}
 
-	list_for_each_entry(pos, &component->card->snd_card->controls, list) {
-		if (pos->private_data == component &&
-		    !strncmp(name, pos->id.name, sizeof(pos->id.name)))
+	list_for_each_entry(iter, &component->card->snd_card->controls, list) {
+		if (iter->private_data == component &&
+		    !strncmp(name, iter->id.name, sizeof(iter->id.name))) {
+			pos = iter;
 			break;
+		}
 	}
-	if (list_entry_is_head(pos, &component->card->snd_card->controls, list))
+	if (!pos)
 		return -ENOENT;
 
 	if (stream->template->type != CATPT_STRM_TYPE_LOOPBACK)

base-commit: f82da161ea75dc4db21b2499e4b1facd36dab275
-- 
2.25.1