linux-hardening - Re: [PATCH v2][next] fsnotify: Avoid -Wflex-array-member-not-at-end warning

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Date: Tue, 26 Mar 2024 10:53:56 +0100
From: Jan Kara <jack@...e.cz>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Jan Kara <jack@...e.cz>, Amir Goldstein <amir73il@...il.com>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH v2][next] fsnotify: Avoid -Wflex-array-member-not-at-end
 warning

On Mon 25-03-24 19:36:02, Gustavo A. R. Silva wrote:
> Use the `DEFINE_FLEX()` helper for an on-stack definition of a
> flexible structure where the size of the flexible-array member
> is known at compile-time, and refactor the rest of the code,
> accordingly.
> 
> So, with these changes, fix the following warning:
> fs/notify/fdinfo.c:45:36: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> Link: https://github.com/KSPP/linux/issues/202
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

Nice! I've added the patch to my tree.

								Honza

> ---
> Changes in v2:
>  - Use DEFINE_FLEX() instead of struct_group_tagged().
> 
> v1:
>  - Link: https://lore.kernel.org/linux-hardening/ZeeaRuTpuxInH6ZB@neat/
> 
>  fs/notify/fdinfo.c | 20 ++++++++------------
>  1 file changed, 8 insertions(+), 12 deletions(-)
> 
> diff --git a/fs/notify/fdinfo.c b/fs/notify/fdinfo.c
> index 5c430736ec12..dec553034027 100644
> --- a/fs/notify/fdinfo.c
> +++ b/fs/notify/fdinfo.c
> @@ -41,29 +41,25 @@ static void show_fdinfo(struct seq_file *m, struct file *f,
>  #if defined(CONFIG_EXPORTFS)
>  static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
>  {
> -	struct {
> -		struct file_handle handle;
> -		u8 pad[MAX_HANDLE_SZ];
> -	} f;
> +	DEFINE_FLEX(struct file_handle, f, f_handle, handle_bytes, MAX_HANDLE_SZ);
>  	int size, ret, i;
>  
> -	f.handle.handle_bytes = sizeof(f.pad);
> -	size = f.handle.handle_bytes >> 2;
> +	size = f->handle_bytes >> 2;
>  
> -	ret = exportfs_encode_fid(inode, (struct fid *)f.handle.f_handle, &size);
> +	ret = exportfs_encode_fid(inode, (struct fid *)f->f_handle, &size);
>  	if ((ret == FILEID_INVALID) || (ret < 0)) {
>  		WARN_ONCE(1, "Can't encode file handler for inotify: %d\n", ret);
>  		return;
>  	}
>  
> -	f.handle.handle_type = ret;
> -	f.handle.handle_bytes = size * sizeof(u32);
> +	f->handle_type = ret;
> +	f->handle_bytes = size * sizeof(u32);
>  
>  	seq_printf(m, "fhandle-bytes:%x fhandle-type:%x f_handle:",
> -		   f.handle.handle_bytes, f.handle.handle_type);
> +		   f->handle_bytes, f->handle_type);
>  
> -	for (i = 0; i < f.handle.handle_bytes; i++)
> -		seq_printf(m, "%02x", (int)f.handle.f_handle[i]);
> +	for (i = 0; i < f->handle_bytes; i++)
> +		seq_printf(m, "%02x", (int)f->f_handle[i]);
>  }
>  #else
>  static void show_mark_fhandle(struct seq_file *m, struct inode *inode)
> -- 
> 2.34.1
> 
-- 
Jan Kara <jack@...e.com>
SUSE Labs, CR