linux-kernel - Re: [PATCH 1/2] media: dvb-usb: Fix memory leak at error in dvb_usb_device

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Date:   Mon, 01 Feb 2021 09:18:32 +0100
From:   Takashi Iwai <tiwai@...e.de>
To:     Sean Young <sean@...s.org>
Cc:     Mauro Carvalho Chehab <mchehab@...nel.org>,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        Stefan Seyfried <seife+kernel@...systems.com>
Subject: Re: [PATCH 1/2] media: dvb-usb: Fix memory leak at error in dvb_usb_device_init()

On Sun, 31 Jan 2021 15:53:20 +0100,
Sean Young wrote:
> 
> On Wed, Jan 20, 2021 at 11:20:56AM +0100, Takashi Iwai wrote:
> > dvb_usb_device_init() allocates a dvb_usb_device object, but it
> > doesn't release it even when returning an error.  The callers don't
> > seem caring it as well, hence those memories are leaked.
> > 
> > This patch assures releasing the memory at the error path in
> > dvb_usb_device_init().  Also it makes sure that USB intfdata is reset
> > and don't return the bogus pointer to the caller at the error path,
> > too.
> > 
> > Cc: <stable@...r.kernel.org>
> > Signed-off-by: Takashi Iwai <tiwai@...e.de>
> > ---
> >  drivers/media/usb/dvb-usb/dvb-usb-init.c | 18 ++++++++++++------
> >  1 file changed, 12 insertions(+), 6 deletions(-)
> > 
> > diff --git a/drivers/media/usb/dvb-usb/dvb-usb-init.c b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> > index c1a7634e27b4..5befec87f26a 100644
> > --- a/drivers/media/usb/dvb-usb/dvb-usb-init.c
> > +++ b/drivers/media/usb/dvb-usb/dvb-usb-init.c
> > @@ -281,15 +281,21 @@ int dvb_usb_device_init(struct usb_interface *intf,
> >  
> >  	usb_set_intfdata(intf, d);
> >  
> > -	if (du != NULL)
> > +	ret = dvb_usb_init(d, adapter_nums);
> 
> dvb_usb_init() has different errors paths. 
> 
> 1. It can return -ENOMEM if it cannot kzalloc(). No other side affects.
> 2. It can return an error if dvb_usb_i2c_init() or dvb_usb_adapter_init()
>    fails. In this case, dvb_usb_exit() is called, which frees 
>    struct dvb_usb_device*
> 
> In the last case we now have a double free.

A good catch, indeed the function has inconsistent behavior.
I'll update the patch and resubmit to address it.


thanks,

Takashi