Re: [PATCH v2] ocxl: Fix potential memory leak on context creation

[Greg Kurz <groug@kaod.org>]

On Mon, 20 May 2019 09:16:18 +0200
Frederic Barrat <fbarrat@linux.ibm.com> wrote:

> If we couldn't fully init a context, we were leaking memory.
> 
> Fixes: b9721d275cc2 ("ocxl: Allow external drivers to use OpenCAPI contexts")

Oops... missed that during review :-\

> Signed-off-by: Frederic Barrat <fbarrat@linux.ibm.com>
> ---
> 
> Changelog:
> v2: reset context pointer in case of allocation failure (Andrew)
> 

Alternatively you could change the code to do:

	ctx = kzalloc(sizeof(struct ocxl_context), GFP_KERNEL);
	if (!ctx)
		return -ENOMEM;
	.
	.
	.
	if (pasid < 0) {
		mutex_unlock(&afu->contexts_lock);
		kfree(ctx);
		return pasid;
	}
	.
	.
	.
	*context = ctx;
	return 0;
}

This has the advantage of clearing any risk of side-effect with
*context forever, which is a safer practice IMHO.

Patch is correct anyway, so:

Reviewed-by: Greg Kurz <groug@kaod.org>

>  drivers/misc/ocxl/context.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/drivers/misc/ocxl/context.c b/drivers/misc/ocxl/context.c
> index bab9c9364184..24e4fb010275 100644
> --- a/drivers/misc/ocxl/context.c
> +++ b/drivers/misc/ocxl/context.c
> @@ -22,6 +22,8 @@ int ocxl_context_alloc(struct ocxl_context **context, struct ocxl_afu *afu,
>  			afu->pasid_base + afu->pasid_max, GFP_KERNEL);
>  	if (pasid < 0) {
>  		mutex_unlock(&afu->contexts_lock);
> +		kfree(*context);
> +		*context = NULL;
>  		return pasid;
>  	}
>  	afu->pasid_count++;