[alsa-devel] [PATCH v2 3/9] ALSA: caiaq: Add a sanity check for invalid EPs

[Johan Hovold]

On Wed, Oct 11, 2017 at 04:40:36PM +0200, Takashi Iwai wrote:
> On Wed, 11 Oct 2017 16:20:31 +0200,
> Johan Hovold wrote:

> > Unrelated to this patch, but this driver fails to kill the ep1_in_urb
> > (which is submitted in this function) in case of later probe errors.
> > This can lead to use-after-free or crashes in the completion callback.
> 
> Yes, a good catch.  Below is the fix patch.

> -- 8< --
> From: Takashi Iwai <tiwai at suse.de>
> Subject: [PATCH] ALSA: caiaq: Fix stray URB at probe error path
> 
> caiaq driver doesn't kill the URB properly at its error path during
> the probe, which may lead to a use-after-free error later.  This patch
> addresses it.
> 
> Reported-by: Johan Hovold <johan at kernel.org>
> Signed-off-by: Takashi Iwai <tiwai at suse.de>

Looks good to me:

Reviewed-by: Johan Hovold <johan at kernel.org>

> ---
>  sound/usb/caiaq/device.c | 12 +++++++++---
>  1 file changed, 9 insertions(+), 3 deletions(-)
> 
> diff --git a/sound/usb/caiaq/device.c b/sound/usb/caiaq/device.c
> index a29674bf96e5..d55ca48de3ea 100644
> --- a/sound/usb/caiaq/device.c
> +++ b/sound/usb/caiaq/device.c
> @@ -476,10 +476,12 @@ static int init_card(struct snd_usb_caiaqdev *cdev)
>  
>  	err = snd_usb_caiaq_send_command(cdev, EP1_CMD_GET_DEVICE_INFO, NULL, 0);
>  	if (err)
> -		return err;
> +		goto err_kill_urb;
>  
> -	if (!wait_event_timeout(cdev->ep1_wait_queue, cdev->spec_received, HZ))
> -		return -ENODEV;
> +	if (!wait_event_timeout(cdev->ep1_wait_queue, cdev->spec_received, HZ)) {
> +		err = -ENODEV;
> +		goto err_kill_urb;
> +	}
>  
>  	usb_string(usb_dev, usb_dev->descriptor.iManufacturer,
>  		   cdev->vendor_name, CAIAQ_USB_STR_LEN);
> @@ -514,6 +516,10 @@ static int init_card(struct snd_usb_caiaqdev *cdev)
>  
>  	setup_card(cdev);
>  	return 0;
> +
> + err_kill_urb:
> +	usb_kill_urb(&cdev->ep1_in_urb);
> +	return err;
>  }
>  
>  static int snd_probe(struct usb_interface *intf,