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 for linux-mtd@lists.infradead.org; Wed, 04 Apr 2018 07:08:45 +0000
Date: Wed, 4 Apr 2018 09:08:31 +0200
From: Boris Brezillon <boris.brezillon@bootlin.com>
To: Miquel Raynal <miquel.raynal@bootlin.com>, Marc Gonzalez
 <marc.w.gonzalez@free.fr>
Cc: Xidong Wang <wangxidong_97@163.com>, Mans Rullgard <mans@mansr.com>,
 Marek Vasut <marek.vasut@gmail.com>, Richard Weinberger <richard@nod.at>,
 linux-mtd@lists.infradead.org, Cyrille Pitchen
 <cyrille.pitchen@wedev4u.fr>, Brian Norris <computersforpeace@gmail.com>,
 David Woodhouse <dwmw2@infradead.org>
Subject: Re: [PATCH 1/1] mtd:nand:fix memory leak
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On Wed, 4 Apr 2018 09:07:10 +0200
Boris Brezillon <boris.brezillon@bootlin.com> wrote:

> On Wed, 4 Apr 2018 08:28:07 +0200
> Miquel Raynal <miquel.raynal@bootlin.com> wrote:
> 
> > Hi Xidong,
> > 
> > As part of a reorganization in the NAND subsystem, you should now
> > prefix your commit title this way:
> > 
> >         mtd: rawnand: tango: fix memory leak
> > 
> > Not sure if this patch is candidate to cc:stable?
> > 
> > On Wed,  4 Apr 2018 11:05:51 +0800, Xidong Wang
> > <wangxidong_97@163.com> wrote:
> >   
> > > In function tango_nand_probe(), the memory allocated by
> > > clk_get() is not released on the normal path and
> > > the error path that IS_ERR(nfc->chan) returns true.    
> > 
> > The fact that the error path returns true looks out of topic, can you
> > remove it? Just saying that you fix a memory leak is enough I guess.
> >   
> > > This will result in a memory leak bug.
> > > 
> > > Signed-off-by: Xidong Wang <wangxidong_97@163.com>
> > > ---
> > >  drivers/mtd/nand/tango_nand.c | 5 ++++-
> > >  1 file changed, 4 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/drivers/mtd/nand/tango_nand.c b/drivers/mtd/nand/tango_nand.c
> > > index c5bee00b..8083459 100644
> > > --- a/drivers/mtd/nand/tango_nand.c
> > > +++ b/drivers/mtd/nand/tango_nand.c
> > > @@ -648,12 +648,15 @@ static int tango_nand_probe(struct platform_device *pdev)
> > >  		return PTR_ERR(clk);
> > >  
> > >  	nfc->chan = dma_request_chan(&pdev->dev, "rxtx");
> > > -	if (IS_ERR(nfc->chan))
> > > +	if (IS_ERR(nfc->chan)) {
> > > +		clk_put(clk);
> > >  		return PTR_ERR(nfc->chan);
> > > +	}
> > >  
> > >  	platform_set_drvdata(pdev, nfc);
> > >  	nand_hw_control_init(&nfc->hw);
> > >  	nfc->freq_kHz = clk_get_rate(clk) / 1000;
> > > +	clk_put(clk);    
> > 
> > If the clock is used only here, better do the frequency derivation
> > right after the clock_get(), and follow with a clk_put()? This way you
> > don't have to change the error path and 'related' actions remain
> > grouped.  
> 
> Hm, definitely not a good idea to release the reference you have on the
> clk if the driver depends on it. I recommend using devm_clk_get() to
> solve this leak.
> 

BTW, it's also weird that the driver does not prepare_enable the clk.
Mark, any comments?