linux-kernel - Re: [PATCH] dmaengine: imx-sdma: fix use-after-free on probe error path

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Message-ID: <20190705124646.GD2911@vkoul-mobl>
Date:   Fri, 5 Jul 2019 18:16:46 +0530
From:   Vinod Koul <vkoul@...nel.org>
To:     Sven Van Asbroeck <thesven73@...il.com>
Cc:     Robin Gong <yibin.gong@....com>,
        Dan Williams <dan.j.williams@...el.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        dmaengine@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] dmaengine: imx-sdma: fix use-after-free on probe error
 path

On 24-06-19, 10:07, Sven Van Asbroeck wrote:

Quoting orignal patch for better context:

> +	if (pdata) {
> +		ret = sdma_get_firmware(sdma, pdata->fw_name);
> +		if (ret)
> +			dev_warn(&pdev->dev, "failed to get firmware from platform data\n");
> +	} else {
> +		/*
> +		 * Because that device tree does not encode ROM script address,
> +		 * the RAM script in firmware is mandatory for device tree
> +		 * probe, otherwise it fails.
> +		 */
> +		ret = of_property_read_string(np, "fsl,sdma-ram-script-name",
> +					      &fw_name);
> +		if (ret)
> +			dev_warn(&pdev->dev, "failed to get firmware name\n");
> +		else {
> +			ret = sdma_get_firmware(sdma, fw_name);
> +			if (ret)
> +				dev_warn(&pdev->dev, "failed to get firmware from device tree\n");
> +		}
> +	}
> +

On 05-07-19, 08:26, Sven Van Asbroeck wrote:
> Hi Vinod,
> 
> On Fri, Jul 5, 2019 at 3:32 AM Vinod Koul <vkoul@...nel.org> wrote:
> >
> > > +             if (ret)
> > > +                     dev_warn(&pdev->dev, "failed to get firmware name\n");
> >
> > if should have braces!
> > Applied after fixing braces!
> 
> checkpatch.pl output after adding braces:
> 
> WARNING: braces {} are not necessary for single statement blocks
> #102: FILE: drivers/dma/imx-sdma.c:2165:
> + if (ret) {
> + dev_warn(&pdev->dev, "failed to get firmware from device tree\n");
> + }

there is an else here too!

With the patch the checkpatch warns:

CHECK: braces {} should be used on all arms of this statement
#201: FILE: drivers/dma/imx-sdma.c:2161:
+		if (ret)
[...]
+		else {
[...]


Even if the if is a single block and else being multi block, if would
need matching brances. With the change pushed:

total: 0 errors, 0 warnings, 0 checks, 60 lines checked


-- 
~Vinod