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

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Message-ID: <20210131145320.GA4886@gofer.mess.org>
Date:   Sun, 31 Jan 2021 14:53:20 +0000
From:   Sean Young <sean@...s.org>
To:     Takashi Iwai <tiwai@...e.de>
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 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.


Sean

> +	if (ret) {
> +		info("%s error while loading driver (%d)", desc->name, ret);
> +		goto error;
> +	}
> +
> +	if (du)
>  		*du = d;
>  
> -	ret = dvb_usb_init(d, adapter_nums);
> +	info("%s successfully initialized and connected.", desc->name);
> +	return 0;
>  
> -	if (ret == 0)
> -		info("%s successfully initialized and connected.", desc->name);
> -	else
> -		info("%s error while loading driver (%d)", desc->name, ret);
> + error:
> +	usb_set_intfdata(intf, NULL);
> +	kfree(d);
>  	return ret;
>  }
>  EXPORT_SYMBOL(dvb_usb_device_init);

> -- 
> 2.26.2