Re: [PATCH][next] ocfs2: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper

From: Kees Cook <keescook@chromium.org>
To: "Gustavo A. R. Silva" <gustavoars@kernel.org>
Cc: Mark Fasheh <mark@fasheh.com>, Joel Becker <jlbec@evilplan.org>,
	Joseph Qi <joseph.qi@linux.alibaba.com>,
	ocfs2-devel@oss.oracle.com, linux-kernel@vger.kernel.org,
	linux-hardening@vger.kernel.org
Subject: Re: [PATCH][next] ocfs2: Replace zero-length arrays with DECLARE_FLEX_ARRAY() helper
Date: Fri, 2 Sep 2022 22:12:25 -0700	[thread overview]
Message-ID: <202209022212.7F753284@keescook> (raw)
In-Reply-To: <YxKY6O2hmdwNh8r8@work>

On Sat, Sep 03, 2022 at 12:59:36AM +0100, Gustavo A. R. Silva wrote:
> Zero-length arrays are deprecated and we are moving towards adopting
> C99 flexible-array members, instead. So, replace zero-length array
> declarations in a couple of structures and unions with the new
> DECLARE_FLEX_ARRAY() helper macro.
> 
> This helper allows for a flexible-array member in a union and as
> only member in a structure.
> 
> Also, this addresses multiple warnings reported when building with
> Clang-15 and -Wzero-length-array.
> 
> Lastly, this will also help memcpy (in a coming hardening update)
> execute proper bounds-checking on variable length object i_symlink
> at fs/ocfs2/namei.c:1973:
> 
> fs/ocfs2/namei.c:
> 1973                 memcpy((char *) fe->id2.i_symlink, symname, l);
> 
> Link: https://github.com/KSPP/linux/issues/21
> Link: https://github.com/KSPP/linux/issues/193
> Link: https://github.com/KSPP/linux/issues/197
> Link: https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
> Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>

Reviewed-by: Kees Cook <keescook@chromium.org>

-- 
Kees Cook