linux-hardening - Re: [PATCH][next] ocfs2: Replace zero-length arrays with DECLARE_FLEX

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Date:   Fri, 2 Sep 2022 22:12:25 -0700
From:   Kees Cook <keescook@...omium.org>
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@....oracle.com, linux-kernel@...r.kernel.org,
        linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] ocfs2: Replace zero-length arrays with
 DECLARE_FLEX_ARRAY() helper

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@...nel.org>

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

-- 
Kees Cook