Re: [2/2] ASoC: samsung: odroid: fix a double-free issue for cpu_dai

Re: [2/2] ASoC: samsung: odroid: fix a double-free issue for cpu_dai

[Markus Elfring]

> These two updates fix two different bugs.

I can follow this view to some degree.


> and the other is the double-free issue

This programming error affects also the use of data structures which became invalid.
https://cwe.mitre.org/data/definitions/415.html#oc_415_Notes


> So we sent two patches to fix them separately.

You would like to fix something according to two variables (of the data type “device_node *”)
in the same function implementation.
Please combine these corrections in an update step under a topic like
“ASoC: samsung: odroid: Fix handling of device node references in odroid_audio_probe()”.
(The previous update step would contain still a known programming mistake otherwise,
wouldn't it?)

Regards,
Markus

[PATCH 2/2] ASoC: samsung: odroid: fix a double-free issue for cpu_dai

[Wen Yang]

The cpu_dai variable is still being used after the of_node_put() call,
which may result in double-free:

        of_node_put(cpu_dai);            ---> released here

        ret = devm_snd_soc_register_card(dev, card);
        if (ret < 0) {
...
                goto err_put_clk_i2s;    --> jump to err_put_clk_i2s
...

err_put_clk_i2s:
        clk_put(priv->clk_i2s_bus);
err_put_sclk:
        clk_put(priv->sclk_i2s);
err_put_cpu_dai:
        of_node_put(cpu_dai);            --> double-free here

Fixes: d832d2b246c5 ("ASoC: samsung: odroid: Fix of_node refcount unbalance")
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
Cc: Krzysztof Kozlowski <krzk@kernel.org>
Cc: Sangbeom Kim <sbkim73@samsung.com>
Cc: Sylwester Nawrocki <s.nawrocki@samsung.com>
Cc: Liam Girdwood <lgirdwood@gmail.com>
Cc: Mark Brown <broonie@kernel.org>
Cc: Jaroslav Kysela <perex@perex.cz>
Cc: Takashi Iwai <tiwai@suse.com>
Cc: alsa-devel@alsa-project.org
Cc: linux-kernel@vger.kernel.org
---
 sound/soc/samsung/odroid.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sound/soc/samsung/odroid.c b/sound/soc/samsung/odroid.c
index 64ebe89..f0f5fa9 100644
--- a/sound/soc/samsung/odroid.c
+++ b/sound/soc/samsung/odroid.c
@@ -308,7 +308,6 @@ static int odroid_audio_probe(struct platform_device *pdev)
 		ret = PTR_ERR(priv->clk_i2s_bus);
 		goto err_put_sclk;
 	}
-	of_node_put(cpu_dai);
 
 	ret = devm_snd_soc_register_card(dev, card);
 	if (ret < 0) {
@@ -316,6 +315,7 @@ static int odroid_audio_probe(struct platform_device *pdev)
 		goto err_put_clk_i2s;
 	}
 
+	of_node_put(cpu_dai);
 	of_node_put(codec);
 	return 0;
 
-- 
2.9.5

Re: [2/2] ASoC: samsung: odroid: fix a double-free issue for cpu_dai

[Markus Elfring]

> The cpu_dai variable is still being used after the of_node_put() call,

Such an implementation detail is questionable.
https://wiki.sei.cmu.edu/confluence/display/c/MEM30-C.+Do+not+access+freed+memory


> which may result in double-free:

This consequence is also undesirable.
https://cwe.mitre.org/data/definitions/415.html


Now I wonder if two update steps are really appropriate as a fix
instead of using a single update step for the desired correction
in this software module.
Should a commit (including previous ones) usually be correct by itself?

Regards,
Markus