linux-kernel - Re: [PATCH] Mtd: nand - Fix possible NULL derefrence.

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Message-ID: <20170127134448.67c1d128@bbrezillon>
Date:   Fri, 27 Jan 2017 13:44:48 +0100
From:   Boris Brezillon <boris.brezillon@...e-electrons.com>
To:     Marek Vasut <marek.vasut@...il.com>
Cc:     Shailendra Verma <shailendra.v@...sung.com>,
        Richard Weinberger <richard@....at>,
        David Woodhouse <dwmw2@...radead.org>,
        Brian Norris <computersforpeace@...il.com>,
        Cyrille Pitchen <cyrille.pitchen@...el.com>,
        linux-mtd@...ts.infradead.org, linux-kernel@...r.kernel.org,
        p.shailesh@...sung.com, ashish.kalra@...sung.com,
        Shailendra Verma <shailendra.capricorn@...il.com>
Subject: Re: [PATCH] Mtd: nand - Fix possible NULL derefrence.

On Fri, 27 Jan 2017 13:24:18 +0100
Marek Vasut <marek.vasut@...il.com> wrote:

> On 01/27/2017 12:29 PM, Shailendra Verma wrote:
> > of_match_device could return NULL, and so can cause a NULL
> > pointer dereference later.
> > 

That's a purely hypothetical bug since the core already matched
against one of the compatible in the of_match table to decide to attach
the device to this driver. Having of_match_device() return NULL here
means something went seriously wrong (memory corruption ?).

This being said, I'm not strongly opposed to this patch. Just a minor
comment below.

Thanks,

Boris

> > Signed-off-by: Shailendra Verma <shailendra.v@...sung.com>  
> 
> Nice find, but can you split this into two patches ? And the prefix is
> 'mtd' without capital letter.
> 
> Thanks
> 
> > ---
> >  drivers/mtd/nand/mxc_nand.c  |    4 ++++
> >  drivers/mtd/nand/vf610_nfc.c |    4 ++++
> >  2 files changed, 8 insertions(+)
> > 
> > diff --git a/drivers/mtd/nand/mxc_nand.c b/drivers/mtd/nand/mxc_nand.c
> > index d7f724b..ca1b8ad 100644
> > --- a/drivers/mtd/nand/mxc_nand.c
> > +++ b/drivers/mtd/nand/mxc_nand.c
> > @@ -1596,6 +1596,10 @@ static int __init mxcnd_probe_dt(struct mxc_nand_host *host)
> >  	if (!np)
> >  		return 1;
> >  
> > +	if (!of_id) {
> > +		dev_err(host->dev, "Error: No device match found\n");
> > +		return -ENODEV;
> > +	}

Add an empty line here.

> >  	host->devtype_data = of_id->data;
> >  
> >  	return 0;
> > diff --git a/drivers/mtd/nand/vf610_nfc.c b/drivers/mtd/nand/vf610_nfc.c
> > index 3ad514c..0e09c11 100644
> > --- a/drivers/mtd/nand/vf610_nfc.c
> > +++ b/drivers/mtd/nand/vf610_nfc.c
> > @@ -674,6 +674,10 @@ static int vf610_nfc_probe(struct platform_device *pdev)
> >  	}
> >  
> >  	of_id = of_match_device(vf610_nfc_dt_ids, &pdev->dev);
> > +	if (!of_id) {
> > +		dev_err(&pdev->dev, "Error: No device match found\n");
> > +		return -ENODEV;
> > +	}

Ditto.

> >  	nfc->variant = (enum vf610_nfc_variant)of_id->data;
> >  
> >  	for_each_available_child_of_node(nfc->dev->of_node, child) {
> >   
> 
>