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

device_register() includes device_add(). As comment of device_add()
says, 'if device_add() succeeds, you should call device_del() when you
want to get rid of it. If device_add() has not succeeded, use only
put_device() to drop the reference count'.

Found by code review.

Cc: stable@vger.kernel.org
Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
Signed-off-by: Ma Ke <make24@iscas.ac.cn>
---
Changes in v2:
- modified the patch as suggestions.
---
 arch/arm/common/locomo.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/arm/common/locomo.c b/arch/arm/common/locomo.c
index 309b74783468..9e48cbb2568e 100644
--- a/arch/arm/common/locomo.c
+++ b/arch/arm/common/locomo.c
@@ -253,6 +253,8 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
 
 	ret = device_register(&dev->dev);
 	if (ret) {
+		put_device(&dev->dev);
+		return ret;
  out:
 		kfree(dev);
 	}
-- 
2.25.1

On Mon, Jan 06, 2025 at 03:47:43PM +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.
> 
> device_register() includes device_add(). As comment of device_add()
> says, 'if device_add() succeeds, you should call device_del() when you
> want to get rid of it. If device_add() has not succeeded, use only
> put_device() to drop the reference count'.
> 
> Found by code review.
> 
> Cc: stable@vger.kernel.org
> Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2")
> Signed-off-by: Ma Ke <make24@iscas.ac.cn>
> ---
> Changes in v2:
> - modified the patch as suggestions.
> ---
>  arch/arm/common/locomo.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/arch/arm/common/locomo.c b/arch/arm/common/locomo.c
> index 309b74783468..9e48cbb2568e 100644
> --- a/arch/arm/common/locomo.c
> +++ b/arch/arm/common/locomo.c
> @@ -253,6 +253,8 @@ locomo_init_one_child(struct locomo *lchip, struct locomo_dev_info *info)
>  
>  	ret = device_register(&dev->dev);
>  	if (ret) {
> +		put_device(&dev->dev);
> +		return ret;
>   out:
>  		kfree(dev);
>  	}

This makes the code layout quite horrible.

Instead, I suggest:

	dev = kzalloc(sizeof(...)...
-	if (!dev) {
-		ret = -ENOMEM;
-		goto out;
-	}
+	if (!dev)
+		return -ENOMEM;

...

	ret = device_register(&dev->dev);
-	if (ret) {
- out:
-		kfree(dev);
-	}
+	if (ret)
+		put_device(&dev->dev);

Thanks.

-- 
RMK's Patch system: https://www.armlinux.org.uk/developer/patches/
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