Re: [PATCH] counter: fix an IS_ERR() vs NULL bug

[William Breathitt Gray <vilhelm.gray@gmail.com>]

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On Tue, Jan 11, 2022 at 10:25:00AM +0300, Dan Carpenter wrote:
> There are 8 callers for devm_counter_alloc() and they all check for NULL
> instead of error pointers.  I think NULL is the better thing to return
> for allocation functions so update counter_alloc() and devm_counter_alloc()
> to return NULL instead of error pointers.
> 
> Fixes: c18e2760308e ("counter: Provide alternative counter registration functions")
> Signed-off-by: Dan Carpenter <dan.carpenter@oracle.com>

Hi Dan,

Thank you for catching this bug. I do request a minor adjustment to this
patch for the sake of matching the format of the rest of the code in
this file: please remove the goto err_alloc_ch and simply exit early
with a return NULL.

> ---
>  drivers/counter/counter-core.c | 12 +++++-------
>  1 file changed, 5 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/counter/counter-core.c b/drivers/counter/counter-core.c
> index 7e0957eea094..0abb28cd3d16 100644
> --- a/drivers/counter/counter-core.c
> +++ b/drivers/counter/counter-core.c
> @@ -90,10 +90,8 @@ struct counter_device *counter_alloc(size_t sizeof_priv)
>  	int err;
>  
>  	ch = kzalloc(sizeof(*ch) + sizeof_priv, GFP_KERNEL);
> -	if (!ch) {
> -		err = -ENOMEM;
> +	if (!ch)
>  		goto err_alloc_ch;

So return NULL here.

> -	}
>  
>  	counter = &ch->counter;
>  	dev = &counter->dev;
> @@ -125,7 +123,7 @@ struct counter_device *counter_alloc(size_t sizeof_priv)
>  	kfree(ch);
>  err_alloc_ch:

Remove this label.

Thank you,

William Breathitt Gray

>  
> -	return ERR_PTR(err);
> +	return NULL;
>  }
>  EXPORT_SYMBOL_GPL(counter_alloc);
>  
> @@ -208,12 +206,12 @@ struct counter_device *devm_counter_alloc(struct device *dev, size_t sizeof_priv
>  	int err;
>  
>  	counter = counter_alloc(sizeof_priv);
> -	if (IS_ERR(counter))
> -		return counter;
> +	if (!counter)
> +		return NULL;
>  
>  	err = devm_add_action_or_reset(dev, devm_counter_put, counter);
>  	if (err < 0)
> -		return ERR_PTR(err);
> +		return NULL;
>  
>  	return counter;
>  }
> -- 
> 2.20.1
> 

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