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From: Hans Verkuil <hverkuil@xs4all.nl>
To: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>,
	linux-media@vger.kernel.org
Cc: dafna3@gmail.com, helen.koike@collabora.com,
	ezequiel@collabora.com, stable@vger.kernel.org
Subject: Re: [PATCH v3] media: v4l2-core: fix a use-after-free bug of sd->devnode
Date: Thu, 16 Jan 2020 12:57:29 +0100	[thread overview]
Message-ID: <fe36e4a9-2369-3150-b823-97fb4bf1afe4@xs4all.nl> (raw)
In-Reply-To: <20191120122217.845-1-dafna.hirschfeld@collabora.com>

On 11/20/19 1:22 PM, Dafna Hirschfeld wrote:
> sd->devnode is released after calling
> v4l2_subdev_release. Therefore it should be set
> to NULL so that the subdev won't hold a pointer
> to a released object. This fixes a reference
> after free bug in function
> v4l2_device_unregister_subdev
> 
> Cc: stable@vger.kernel.org
> Fixes: 0e43734d4c46e ("media: v4l2-subdev: add release() internal op")
> Signed-off-by: Dafna Hirschfeld <dafna.hirschfeld@collabora.com>
> Reviewed-by: Ezequiel Garcia <ezequiel@collabora.com>
> ---
> changes since v2:
> - since this is a regresion fix, I added Fixes and Cc to stable tags,
> - change the commit title and log to be more clear.
> 
>  drivers/media/v4l2-core/v4l2-device.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-device.c b/drivers/media/v4l2-core/v4l2-device.c
> index 63d6b147b21e..2b3595671d62 100644
> --- a/drivers/media/v4l2-core/v4l2-device.c
> +++ b/drivers/media/v4l2-core/v4l2-device.c
> @@ -177,6 +177,7 @@ static void v4l2_subdev_release(struct v4l2_subdev *sd)
>  {
>  	struct module *owner = !sd->owner_v4l2_dev ? sd->owner : NULL;
>  
> +	sd->devnode = NULL;
>  	if (sd->internal_ops && sd->internal_ops->release)
>  		sd->internal_ops->release(sd);

I'd move the sd->devnode = NULL; line here. That way the
sd->internal_ops->release(sd) callback can still use it.

Unless I am missing something?

>  	module_put(owner);
> 

Regards,

	Hans

  reply	other threads:[~2020-01-16 11:57 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-20 12:22 [PATCH v3] media: v4l2-core: fix a use-after-free bug of sd->devnode Dafna Hirschfeld
2020-01-16 11:57 ` Hans Verkuil [this message]
2020-01-17 10:35   ` Dafna Hirschfeld
2020-01-17 10:46     ` Hans Verkuil
2020-01-17 10:52       ` Dafna Hirschfeld
2020-01-31 15:42   ` Ezequiel Garcia

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