Once device_register() failed, we should call put_device() to
decrement reference count for cleanup. Or it could cause memory leak.

As comment of device_register() says, 'NOTE: _Never_ directly free
@dev after calling this function, even if it returned an error! Always
use put_device() to give up the reference initialized in this function
instead.'

Found by code review.

Cc: stable@vger.kernel.org
Fixes: baa057e29b58 ("media: v4l2-dev: use pr_foo() for printing messages")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
 drivers/media/v4l2-core/v4l2-dev.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
index 5bcaeeba4d09..1619614e96bf 100644
--- a/drivers/media/v4l2-core/v4l2-dev.c
+++ b/drivers/media/v4l2-core/v4l2-dev.c
@@ -1060,6 +1060,7 @@ int __video_register_device(struct video_device *vdev,
 	if (ret < 0) {
 		mutex_unlock(&videodev_lock);
 		pr_err("%s: device_register failed\n", __func__);
+		put_device(&vdev->dev);
 		goto cleanup;
 	}
 	/* Register the release callback that will be called when the last
-- 
2.25.1

Hi Ma,

Thanks for the patch.

On Thu, Mar 13, 2025 at 03:43:18PM +0800, Ma Ke wrote:
> Once device_register() failed, we should call put_device() to
> decrement reference count for cleanup. Or it could cause memory leak.
> 
> As comment of device_register() says, 'NOTE: _Never_ directly free
> @dev after calling this function, even if it returned an error! Always
> use put_device() to give up the reference initialized in this function
> instead.'
> 
> Found by code review.
> 
> Cc: stable@vger.kernel.org
> Fixes: baa057e29b58 ("media: v4l2-dev: use pr_foo() for printing messages")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
>  drivers/media/v4l2-core/v4l2-dev.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/drivers/media/v4l2-core/v4l2-dev.c b/drivers/media/v4l2-core/v4l2-dev.c
> index 5bcaeeba4d09..1619614e96bf 100644
> --- a/drivers/media/v4l2-core/v4l2-dev.c
> +++ b/drivers/media/v4l2-core/v4l2-dev.c
> @@ -1060,6 +1060,7 @@ int __video_register_device(struct video_device *vdev,
>  	if (ret < 0) {
>  		mutex_unlock(&videodev_lock);
>  		pr_err("%s: device_register failed\n", __func__);
> +		put_device(&vdev->dev);

Fixing this isn't quite as simple. The release callback is actually set
below so there's no release callback set for this device yet.

>  		goto cleanup;
>  	}
>  	/* Register the release callback that will be called when the last

-- 
Kind regards,

Sakari Ailus