linux-kernel - Re: [PATCH] media: em28xx: return error on media_device

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Date: Thu, 11 Jan 2024 07:49:05 +0100
From: Mauro Carvalho Chehab <mchehab@...nel.org>
To: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
Cc: <linux-media@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] media: em28xx: return error on media_device_register()
 failure

Em Wed, 10 Jan 2024 09:39:58 -0800
Nikita Zhandarovich <n.zhandarovich@...tech.ru> escreveu:

> In an unlikely case of failure in media_device_register(), release
> resources and return the erroneous value. Otherwise, possible issues
> with registering the device will continue to be ignored.
> 
> Found by Linux Verification Center (linuxtesting.org) with static
> analysis tool SVACE.
> 
> Fixes: 37ecc7b1278f ("[media] em28xx: add media controller support")
> Signed-off-by: Nikita Zhandarovich <n.zhandarovich@...tech.ru>
> ---
>  drivers/media/usb/em28xx/em28xx-cards.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/media/usb/em28xx/em28xx-cards.c b/drivers/media/usb/em28xx/em28xx-cards.c
> index 4d037c92af7c..dae731dfc569 100644
> --- a/drivers/media/usb/em28xx/em28xx-cards.c
> +++ b/drivers/media/usb/em28xx/em28xx-cards.c
> @@ -4095,6 +4095,8 @@ static int em28xx_usb_probe(struct usb_interface *intf,
>  	 */
>  #ifdef CONFIG_MEDIA_CONTROLLER
>  	retval = media_device_register(dev->media_dev);
> +	if (retval)
> +		goto err_free;

Not freeing resources here is intentional. See, the media controller 
API is optional on this driver. It will just provide a way to identify
the device's topology, but the device is completely usable without
it.

Perhaps we need, instead, a patch documenting it, and preventing
static analysis tools to point it as an issue.

Thanks,
Mauro