linux-kernel - Re: [PATCH v2] ARM: imx: fix error handling

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Message-ID: <20140516231855.GB4323@lianli>
Date:	Sat, 17 May 2014 01:18:55 +0200
From:	Emil Goode <emilgoode@...il.com>
To:	Uwe Kleine-König <u.kleine-koenig@...gutronix.de>
Cc:	Shawn Guo <shawn.guo@...escale.com>,
	Sascha Hauer <kernel@...gutronix.de>,
	Russell King <linux@....linux.org.uk>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	kernel-janitors@...r.kernel.org
Subject: Re: [PATCH v2] ARM: imx: fix error handling

Hello Uwe,

Thank you for the review.

On Fri, May 16, 2014 at 09:24:51PM +0200, Uwe Kleine-König wrote:
> Hello Emil,
> 
> IMHO the subject is too general. Maybe better use:
> 
> 	ARM: imx: fix error handling in ipu device registration

Agreed, will change this and resend.

> 
> On Fri, May 16, 2014 at 11:54:05AM +0200, Emil Goode wrote:
> > If we fail to allocate struct platform_device pdev we
> > dereference it after the goto label err.
> > 
> > I have rearranged the error handling a bit to fix the issue
> > and also make it more clear.
> > 
> > Signed-off-by: Emil Goode <emilgoode@...il.com>
> > ---
> > v2: Changed to return -ENOMEM instead of ret where possible and
> >     updated the subject line.
> > 
> >  arch/arm/mach-imx/devices/platform-ipu-core.c |   22 +++++++++++++---------
> >  1 file changed, 13 insertions(+), 9 deletions(-)
> > 
> > diff --git a/arch/arm/mach-imx/devices/platform-ipu-core.c b/arch/arm/mach-imx/devices/platform-ipu-core.c
> > index fc4dd7c..68f2a4a 100644
> > --- a/arch/arm/mach-imx/devices/platform-ipu-core.c
> > +++ b/arch/arm/mach-imx/devices/platform-ipu-core.c
> > @@ -77,34 +77,38 @@ struct platform_device *__init imx_alloc_mx3_camera(
> >  
> >  	pdev = platform_device_alloc("mx3-camera", 0);
> >  	if (!pdev)
> > -		goto err;
> > +		return ERR_PTR(-ENOMEM);
> >  
> >  	pdev->dev.dma_mask = kmalloc(sizeof(*pdev->dev.dma_mask), GFP_KERNEL);
> >  	if (!pdev->dev.dma_mask)
> > -		goto err;
> > +		goto put_pdev;
> >  
> >  	*pdev->dev.dma_mask = DMA_BIT_MASK(32);
> >  	pdev->dev.coherent_dma_mask = DMA_BIT_MASK(32);
> >  
> >  	ret = platform_device_add_resources(pdev, res, ARRAY_SIZE(res));
> >  	if (ret)
> > -		goto err;
> > +		goto free_dma_mask;
> >  
> >  	if (pdata) {
> >  		struct mx3_camera_pdata *copied_pdata;
> >  
> >  		ret = platform_device_add_data(pdev, pdata, sizeof(*pdata));
> > -		if (ret) {
> > -err:
> > -			kfree(pdev->dev.dma_mask);
> > -			platform_device_put(pdev);
> > -			return ERR_PTR(-ENODEV);
> > -		}
> > +		if (ret)
> > +			goto free_dma_mask;
> > +
> >  		copied_pdata = dev_get_platdata(&pdev->dev);
> >  		copied_pdata->dma_dev = &imx_ipu_coredev->dev;
> >  	}
> >  
> >  	return pdev;
> > +
> > +free_dma_mask:
> > +	kfree(pdev->dev.dma_mask);
> > +put_pdev:
> > +	platform_device_put(pdev);
> > +
> > +	return ERR_PTR(ret);
> >  }
> I didn't check if it is easily possible, but converting this file to use
> platform_device_register_full might simplify it considerably.

Will look into this and consider sending another patch.

> 
> I'm not sure this fix is critical, because the problem happens if an
> allocation during boot fails. But still, if you want to get this fix
> into a stable release, you should simplify it, i.e. don't do the code
> reorganisations. (Also the "more clear" part seems to be subjective, I
> like the error handling better as it is now. But that might only be me.)

To my knowlege there is no impact on end users and I don't think the bug
is critical since, as you say, the allocation happens during boot.
Probably it's not necessary to have this fixed in stable kernels.

> 
> Are you using this code? I thought arch/arm/mach-imx/devices to be dead
> as it is unused on dt platforms.

The bug was found using coccinelle. I'm not using the code and I don't know
what the plans are for this file in the transition to device tree. But as long
as the file is in the kernel I think it's worth fixing the bug.

Best regards,

Emil Goode

> 
> Best regards
> Uwe
> 
> -- 
> Pengutronix e.K.                           | Uwe Kleine-König            |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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