linux-kernel - Re: [PATCH] net: dsa: loop: Check for memory allocation failure

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Message-ID: <alpine.DEB.2.20.1705090745190.3309@hadrien>
Date:   Tue, 9 May 2017 07:46:34 +0800 (SGT)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Joe Perches <joe@...ches.com>
cc:     David Laight <David.Laight@...LAB.COM>,
        'Christophe JAILLET' <christophe.jaillet@...adoo.fr>,
        "andrew@...n.ch" <andrew@...n.ch>,
        "vivien.didelot@...oirfairelinux.com" 
        <vivien.didelot@...oirfairelinux.com>,
        "f.fainelli@...il.com" <f.fainelli@...il.com>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH] net: dsa: loop: Check for memory allocation failure



On Mon, 8 May 2017, Joe Perches wrote:

> On Mon, 2017-05-08 at 20:32 +0800, Julia Lawall wrote:
> >
> > On Mon, 8 May 2017, David Laight wrote:
> >
> > > From: Christophe JAILLET
> > > > Sent: 06 May 2017 06:30
> > > > If 'devm_kzalloc' fails, a NULL pointer will be dereferenced.
> > > > Return -ENOMEM instead, as done for some other memory allocation just a
> > > > few lines above.
> > >
> > > ...
> > > > --- a/drivers/net/dsa/dsa_loop.c
> > > > +++ b/drivers/net/dsa/dsa_loop.c
> > > > @@ -256,6 +256,9 @@ static int dsa_loop_drv_probe(struct mdio_device *mdiodev)
> > > >  		return -ENOMEM;
> > > >
> > > >  	ps = devm_kzalloc(&mdiodev->dev, sizeof(*ps), GFP_KERNEL);
> > > > +	if (!ps)
> > > > +		return -ENOMEM;
> > > > +
> > > >  	ps->netdev = dev_get_by_name(&init_net, pdata->netdev);
> > > >  	if (!ps->netdev)
> > > >  		return -EPROBE_DEFER;
> > >
> > > On the face if it this code leaks like a sieve.
> >
> > I don't think so.  The allocations (dsa_switch_alloc and devm_kzalloc) use
> > devm functions.
>
> It's at least wasteful.
>
> Each time -EPROBE_DEFER occurs, another set of calls to
> dsa_switch_alloc and dev_kzalloc also occurs.
>
> Perhaps it'd be better to do:
>
> 	if (ps->netdev) {
> 		devm_kfree(&devmdev->dev, ps);
> 		devm_kfree(&mdiodev->dev, ds);
> 		return -EPROBE_DEFER;
> 	}

Is EPROBE_DEFER handled differently than other kinds of errors?

julia


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