linux-kernel - Re: [PATCH] kernfs: move return value check after kmalloc()

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Date:   Fri, 21 May 2021 06:39:40 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Austin Kim <austindh.kim@...il.com>
Cc:     tj@...nel.org, neilb@...e.de, linux-kernel@...r.kernel.org,
        austin.kim@....com
Subject: Re: [PATCH] kernfs: move return value check after kmalloc()

On Fri, May 21, 2021 at 03:55:25AM +0100, Austin Kim wrote:
> With 414985ae23c0 ("sysfs, kernfs: move file core code to fs/kernfs/file.c"),
> 'return -ENOMEM' is executed when kmalloc() returns NULL.
> 
> Since 'commit 4ef67a8c95f3 ("sysfs/kernfs: make read requests on pre-alloc
> files use the buffer.")', 'return -ENOMEM' statement is not properly located.
> 
> Fix it by moving 'return -ENOMEM' after return from kmalloc().
> 
> Fixes: 4ef67a8c95f3 ("sysfs/kernfs: make read requests on pre-alloc files use the buffer.")
> Signed-off-by: Austin Kim <austindh.kim@...il.com>
> ---
>  fs/kernfs/file.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
> index c75719312147..c5e2429af836 100644
> --- a/fs/kernfs/file.c
> +++ b/fs/kernfs/file.c
> @@ -191,10 +191,11 @@ static ssize_t kernfs_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
>  	buf = of->prealloc_buf;
>  	if (buf)
>  		mutex_lock(&of->prealloc_mutex);
> -	else
> +	else {
>  		buf = kmalloc(len, GFP_KERNEL);
> -	if (!buf)
> -		return -ENOMEM;
> +		if (!buf)
> +			return -ENOMEM;
> +	}
>  
>  	/*
>  	 * @of->mutex nests outside active ref and is used both to ensure that
> -- 
> 2.20.1
> 

Like Neil said, I don't see the "bug" you are fixing here.  What is
currently wrong with the existing code?

thanks,

greg k-h