linux-kernel - Re: [PATCH 04/11] hso: fix memory leak in hso_create

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Message-ID: <1421779293.681.16.camel@dcbw.local>
Date:	Tue, 20 Jan 2015 12:41:33 -0600
From:	Dan Williams <dcbw@...hat.com>
To:	Oliver Neukum <oneukum@...e.de>
Cc:	Olivier Sobrie <olivier@...rie.be>, Jan Dumon <j.dumon@...ion.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, linux-usb@...r.kernel.org,
	netdev@...r.kernel.org
Subject: Re: [PATCH 04/11] hso: fix memory leak in hso_create_rfkill()

On Tue, 2015-01-20 at 14:13 +0100, Oliver Neukum wrote:
> On Tue, 2015-01-20 at 13:29 +0100, Olivier Sobrie wrote:
> > When the rfkill interface was created, a buffer containing the name
> > of the rfkill node was allocated. This buffer was never freed when the
> > device disappears.
> > 
> > To fix the problem, we put the name given to rfkill_alloc() in
> > the hso_net structure.
> > 
> > Signed-off-by: Olivier Sobrie <olivier@...rie.be>
> > ---
> >  drivers/net/usb/hso.c | 12 +++---------
> >  1 file changed, 3 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/net/usb/hso.c b/drivers/net/usb/hso.c
> > index 470ef9e..a49ac2e 100644
> > --- a/drivers/net/usb/hso.c
> > +++ b/drivers/net/usb/hso.c
> > @@ -153,6 +153,7 @@ struct hso_net {
> >  	struct hso_device *parent;
> >  	struct net_device *net;
> >  	struct rfkill *rfkill;
> > +	char name[8];
> >  
> >  	struct usb_endpoint_descriptor *in_endp;
> >  	struct usb_endpoint_descriptor *out_endp;
> > @@ -2467,27 +2468,20 @@ static void hso_create_rfkill(struct hso_device *hso_dev,
> >  {
> >  	struct hso_net *hso_net = dev2net(hso_dev);
> >  	struct device *dev = &hso_net->net->dev;
> > -	char *rfkn;
> >  
> > -	rfkn = kzalloc(20, GFP_KERNEL);
> > -	if (!rfkn)
> > -		dev_err(dev, "%s - Out of memory\n", __func__);
> > -
> > -	snprintf(rfkn, 20, "hso-%d",
> > +	snprintf(hso_net->name, sizeof(hso_net->name), "hso-%d",
> >  		 interface->altsetting->desc.bInterfaceNumber);
> 
> That number is not unique. Indeed it will be identical for all devices.

I would say just do "static u32 rfkill_counter = 0" and 

+	snprintf(hso_net->name, sizeof(hso_net->name), "hso-%d",
+  		 rfkill_counter++);

We can't just use the netdev's name because that may have conflicts.
eg, the netdev will get hso0 when plugged in (and thus rfkill would get
hso-0) but then udev will rename that to something like wwp0s26f7u2i8.
Then the second HSO you plug in will get the name 'hso0', and so the
second rfkill would get 'hso-0', but that's already taken by the first
rfkill...  Which is why I just suggest a counter.

Dan

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