linux-kernel - Re: [PATCH][next] ocfs2: Avoid -Wflex-array-member-not-at-end warning

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <7vsq3tvjuv3ppiot3lgithyp76r4jbbssoiiuni6zvj5pajsov@nketwax66jss>
Date: Mon, 17 Nov 2025 13:32:01 +0800
From: Heming Zhao <heming.zhao@...e.com>
To: "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc: Mark Fasheh <mark@...heh.com>, Joel Becker <jlbec@...lplan.org>, 
	Joseph Qi <joseph.qi@...ux.alibaba.com>, ocfs2-devel@...ts.linux.dev, linux-kernel@...r.kernel.org, 
	linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] ocfs2: Avoid -Wflex-array-member-not-at-end warning

On Tue, Nov 11, 2025 at 12:01:19PM +0900, Gustavo A. R. Silva wrote:
> -Wflex-array-member-not-at-end was introduced in GCC-14, and we are
> getting ready to enable it, globally.
> 
> Use the new TRAILING_OVERLAP() helper to fix the following warning:
> 
> fs/ocfs2/xattr.c:52:41: warning: structure containing a flexible array member is not at the end of another structure [-Wflex-array-member-not-at-end]
> 
> This helper creates a union between a flexible-array member (FAM) and a
> set of MEMBERS that would otherwise follow it.
> 
> This overlays the trailing MEMBER struct ocfs2_extent_rec er; onto the
> FAM struct ocfs2_xattr_value_root::xr_list.l_recs[], while keeping the
> FAM and the start of MEMBER aligned.
> 
> The static_assert() ensures this alignment remains, and it's
> intentionally placed inmediately after the related structure --no
> blank line in between.
> 
> Signed-off-by: Gustavo A. R. Silva <gustavoars@...nel.org>

LGTM.
Reviewed-by: Heming Zhao <heming.zhao@...e.com>

> ---
>  fs/ocfs2/xattr.c | 8 ++++++--
>  1 file changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/fs/ocfs2/xattr.c b/fs/ocfs2/xattr.c
> index d70a20d29e3e..09069defd7e1 100644
> --- a/fs/ocfs2/xattr.c
> +++ b/fs/ocfs2/xattr.c
> @@ -49,9 +49,13 @@
>  #include "ocfs2_trace.h"
>  
>  struct ocfs2_xattr_def_value_root {
> -	struct ocfs2_xattr_value_root	xv;
> -	struct ocfs2_extent_rec		er;
> +	/* Must be last as it ends in a flexible-array member. */
> +	TRAILING_OVERLAP(struct ocfs2_xattr_value_root, xv, xr_list.l_recs,
> +		struct ocfs2_extent_rec		er;
> +	);
>  };
> +static_assert(offsetof(struct ocfs2_xattr_def_value_root, xv.xr_list.l_recs) ==
> +	      offsetof(struct ocfs2_xattr_def_value_root, er));
>  
>  struct ocfs2_xattr_bucket {
>  	/* The inode these xattrs are associated with */
> -- 
> 2.43.0
> 
>