linux-kernel - Re: [PATCH] fs: Replace offsetof() with struct

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Message-ID: <53c374bjebongkfj5kejf7hb3blgdfvp7e4j4pzahcpw6ubdxp@6vwxcf576ll6>
Date: Fri, 29 Aug 2025 12:39:56 +0200
From: Jan Kara <jack@...e.cz>
To: Xichao Zhao <zhao.xichao@...o.com>
Cc: viro@...iv.linux.org.uk, brauner@...nel.org, jack@...e.cz, 
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] fs: Replace offsetof() with struct_size()

On Fri 29-08-25 18:03:28, Xichao Zhao wrote:
> When dealing with structures containing flexible arrays, struct_size()
> provides additional compile-time checks compared to offsetof(). This
> enhances code robustness and reduces the risk of potential errors.
> 
> Signed-off-by: Xichao Zhao <zhao.xichao@...o.com>

Looks good. Feel free to add:

Reviewed-by: Jan Kara <jack@...e.cz>

								Honza

> ---
>  fs/namei.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/namei.c b/fs/namei.c
> index 10f7caff7f0f..70a71b1b8abc 100644
> --- a/fs/namei.c
> +++ b/fs/namei.c
> @@ -178,7 +178,7 @@ getname_flags(const char __user *filename, int flags)
>  	 * userland.
>  	 */
>  	if (unlikely(len == EMBEDDED_NAME_MAX)) {
> -		const size_t size = offsetof(struct filename, iname[1]);
> +		const size_t size = struct_size(result, iname, 1);
>  		kname = (char *)result;
>  
>  		/*
> @@ -253,7 +253,7 @@ struct filename *getname_kernel(const char * filename)
>  	if (len <= EMBEDDED_NAME_MAX) {
>  		result->name = (char *)result->iname;
>  	} else if (len <= PATH_MAX) {
> -		const size_t size = offsetof(struct filename, iname[1]);
> +		const size_t size = struct_size(result, iname, 1);
>  		struct filename *tmp;
>  
>  		tmp = kmalloc(size, GFP_KERNEL);
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR