linux-kernel - Re: [PATCH][next] net: ethernet: rmnet: Replace zero-length array with DECLARE_FLEX

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Message-ID: <20220926172604.71a20b7d@kernel.org>
Date:   Mon, 26 Sep 2022 17:26:04 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "Gustavo A. R. Silva" <gustavoars@...nel.org>,
        Subash Abhinov Kasiviswanathan <quic_subashab@...cinc.com>,
        Sean Tranchetti <quic_stranche@...cinc.com>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH][next] net: ethernet: rmnet: Replace zero-length array
 with DECLARE_FLEX_ARRAY() helper

On Mon, 26 Sep 2022 15:02:48 -0700 Kees Cook wrote:
> On Mon, Sep 26, 2022 at 04:50:03PM -0500, 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 arrays
> > declarations in anonymous union with the new DECLARE_FLEX_ARRAY()
> > helper macro.
> > 
> > This helper allows for flexible-array members in unions.
> > 
> > Link: https://github.com/KSPP/linux/issues/193
> > Link: https://github.com/KSPP/linux/issues/221
> > 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>

Not directly related to this patch, but I just had to look at pahole
output for sk_buff and the struct_group() stuff makes is really painful
to read :/ Offsets for the members are relative to the "group" and they
are all repeated.

Is there any chance you could fix that? Before we sprinkle more pixie
dust around, perhaps?