linux-hardening - Re: [PATCH v2][next] ASoC: ti: davinci-mcasp: Fix fall-through warning for Clang

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Message-ID: <a0452dc7da2c46e3e764bdd5fd9b94dc96d96912.camel@perches.com>
Date:   Fri, 04 Jun 2021 00:53:04 -0700
From:   Joe Perches <joe@...ches.com>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Peter Ujfalusi <peter.ujfalusi@...il.com>,
        Liam Girdwood <lgirdwood@...il.com>,
        Mark Brown <broonie@...nel.org>,
        Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.com>
Cc:     alsa-devel@...a-project.org, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] ASoC: ti: davinci-mcasp: Fix fall-through
 warning for Clang

On Fri, 2021-06-04 at 02:27 -0500, Gustavo A. R. Silva wrote:
> In preparation to enable -Wimplicit-fallthrough for Clang, fix a warning
> by explicitly adding a fallthrough; statement.
> 
> Link: https://github.com/KSPP/linux/issues/115
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>
> ---
> Changes in v2:
>  - Use fallthrough; instead of break;
>  - Update changelog text.
>  Link: https://lore.kernel.org/linux-hardening/25941c37-6e38-88ae-3afe-4f5af44380d3@gmail.com/
[]
> diff --git a/sound/soc/ti/davinci-mcasp.c b/sound/soc/ti/davinci-mcasp.c
[]
> @@ -2317,6 +2317,7 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
>  		break;
>  	default:
>  		dev_err(&pdev->dev, "No DMA controller found (%d)\n", ret);
> +		fallthrough;
>  	case -EPROBE_DEFER:
>  		goto err;
>  	}

While this is OK, perhaps the below would be clearer and a more common style
as it doesn't intermix default: with logging output and a case label.
---
 sound/soc/ti/davinci-mcasp.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/sound/soc/ti/davinci-mcasp.c b/sound/soc/ti/davinci-mcasp.c
index b94220306d1a8..1059a696ff90e 100644
--- a/sound/soc/ti/davinci-mcasp.c
+++ b/sound/soc/ti/davinci-mcasp.c
@@ -2305,6 +2305,9 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
 		goto err;
 
 	ret = davinci_mcasp_get_dma_type(mcasp);
+	if (ret == -EPROBE_DEFER)
+		goto err;
+
 	switch (ret) {
 	case PCM_EDMA:
 		ret = edma_pcm_platform_register(&pdev->dev);
@@ -2317,7 +2320,6 @@ static int davinci_mcasp_probe(struct platform_device *pdev)
 		break;
 	default:
 		dev_err(&pdev->dev, "No DMA controller found (%d)\n", ret);
-	case -EPROBE_DEFER:
 		goto err;
 	}