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

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Message-ID: <1494265443.31950.62.camel@perches.com>
Date:   Mon, 08 May 2017 10:44:03 -0700
From:   Joe Perches <joe@...ches.com>
To:     Julia Lawall <julia.lawall@...6.fr>,
        David Laight <David.Laight@...LAB.COM>
Cc:     '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, 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;
	}