Re: [PATCH 1/5] media: video-i2c: avoid accessing released memory area when removing driver

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On Mon, Sep 17, 2018 at 9:03 AM Akinobu Mita <akinobu.mita@xxxxxxxxx> wrote:
>
> The struct video_i2c_data is released when video_unregister_device() is
> called, but it will still be accessed after calling
> video_unregister_device().
>
> Use devm_kzalloc() and let the memory be automatically released on driver
> detach.
>
> Fixes: 5cebaac60974 ("media: video-i2c: add video-i2c driver")
> Cc: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>
> Cc: Sakari Ailus <sakari.ailus@xxxxxxxxxxxxxxx>
> Cc: Hans Verkuil <hansverk@xxxxxxxxx>
> Cc: Mauro Carvalho Chehab <mchehab@xxxxxxxxxx>
> Signed-off-by: Akinobu Mita <akinobu.mita@xxxxxxxxx>

Acked-by: Matt Ranostay <matt.ranostay@xxxxxxxxxxxx>

> ---
>  drivers/media/i2c/video-i2c.c | 18 +++++-------------
>  1 file changed, 5 insertions(+), 13 deletions(-)
>
> diff --git a/drivers/media/i2c/video-i2c.c b/drivers/media/i2c/video-i2c.c
> index 06d29d8..b7a2af9 100644
> --- a/drivers/media/i2c/video-i2c.c
> +++ b/drivers/media/i2c/video-i2c.c
> @@ -508,20 +508,15 @@ static const struct v4l2_ioctl_ops video_i2c_ioctl_ops = {
>         .vidioc_streamoff               = vb2_ioctl_streamoff,
>  };
>
> -static void video_i2c_release(struct video_device *vdev)
> -{
> -       kfree(video_get_drvdata(vdev));
> -}
> -
>  static int video_i2c_probe(struct i2c_client *client,
>                              const struct i2c_device_id *id)
>  {
>         struct video_i2c_data *data;
>         struct v4l2_device *v4l2_dev;
>         struct vb2_queue *queue;
> -       int ret = -ENODEV;
> +       int ret;
>
> -       data = kzalloc(sizeof(*data), GFP_KERNEL);
> +       data = devm_kzalloc(&client->dev, sizeof(*data), GFP_KERNEL);
>         if (!data)
>                 return -ENOMEM;
>
> @@ -530,7 +525,7 @@ static int video_i2c_probe(struct i2c_client *client,
>         else if (id)
>                 data->chip = &video_i2c_chip[id->driver_data];
>         else
> -               goto error_free_device;
> +               return -ENODEV;
>
>         data->client = client;
>         v4l2_dev = &data->v4l2_dev;
> @@ -538,7 +533,7 @@ static int video_i2c_probe(struct i2c_client *client,
>
>         ret = v4l2_device_register(&client->dev, v4l2_dev);
>         if (ret < 0)
> -               goto error_free_device;
> +               return ret;
>
>         mutex_init(&data->lock);
>         mutex_init(&data->queue_lock);
> @@ -568,7 +563,7 @@ static int video_i2c_probe(struct i2c_client *client,
>         data->vdev.fops = &video_i2c_fops;
>         data->vdev.lock = &data->lock;
>         data->vdev.ioctl_ops = &video_i2c_ioctl_ops;
> -       data->vdev.release = video_i2c_release;
> +       data->vdev.release = video_device_release_empty;
>         data->vdev.device_caps = V4L2_CAP_VIDEO_CAPTURE |
>                                  V4L2_CAP_READWRITE | V4L2_CAP_STREAMING;
>
> @@ -597,9 +592,6 @@ static int video_i2c_probe(struct i2c_client *client,
>         mutex_destroy(&data->lock);
>         mutex_destroy(&data->queue_lock);
>
> -error_free_device:
> -       kfree(data);
> -
>         return ret;
>  }
>
> --
> 2.7.4
>



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