linux-kernel - Re: [PATCH v2 4/9] staging: android: ion: Avoid NULL point in error path

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Date:   Fri, 16 Feb 2018 17:27:32 +0100
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Yisheng Xie <xieyisheng1@...wei.com>
Cc:     labbott@...hat.com, sumit.semwal@...aro.org,
        devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/9] staging: android: ion: Avoid NULL point in error
 path

On Mon, Feb 12, 2018 at 06:43:09PM +0800, Yisheng Xie wrote:
> If we failed to create debugfs for ion at ion_device_create, the
> debug_root of ion_device will be NULL, and then when try to create debug
> file for shrinker of heap it will be create on the top of debugfs. If we
> also failed to create this the debug file, it call dentry_path to found
> the path of debug_root, then a NULL point will occur.
> 
> Fix this by avoiding call dentry_path, but show the debug name only when
> failed to create debug file for shrinker.
> 
> Acked-by: Laura Abbott <labbott@...hat.com>
> Signed-off-by: Yisheng Xie <xieyisheng1@...wei.com>
> ---
>  drivers/staging/android/ion/ion.c | 10 +++-------
>  1 file changed, 3 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/staging/android/ion/ion.c b/drivers/staging/android/ion/ion.c
> index 57e0d80..4b69372 100644
> --- a/drivers/staging/android/ion/ion.c
> +++ b/drivers/staging/android/ion/ion.c
> @@ -564,13 +564,9 @@ void ion_device_add_heap(struct ion_heap *heap)
>  		debug_file = debugfs_create_file(debug_name,
>  						 0644, dev->debug_root, heap,
>  						 &debug_shrink_fops);
> -		if (!debug_file) {
> -			char buf[256], *path;
> -
> -			path = dentry_path(dev->debug_root, buf, 256);
> -			pr_err("Failed to create heap shrinker debugfs at %s/%s\n",
> -			       path, debug_name);
> -		}
> +		if (!debug_file)
> +			pr_err("Failed to create ion heap shrinker debugfs at %s\n",
> +			       debug_name);

Really we can just remove this, there's no need to check the return
value of this debugfs call at all, it doesn't matter.

thanks,

greg k-h