linux-hardening - Re: [PATCH] af_unix: Silence randstruct GCC plugin warning

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Date:   Wed, 11 May 2022 15:15:42 -0700
From:   Jakub Kicinski <kuba@...nel.org>
To:     Kees Cook <keescook@...omium.org>
Cc:     "David S. Miller" <davem@...emloft.net>,
        Christoph Hellwig <hch@...radead.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Kuniyuki Iwashima <kuniyu@...zon.co.jp>,
        Alexei Starovoitov <ast@...nel.org>,
        Cong Wang <cong.wang@...edance.com>,
        Al Viro <viro@...iv.linux.org.uk>, netdev@...r.kernel.org,
        linux-hardening@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] af_unix: Silence randstruct GCC plugin warning

On Tue, 10 May 2022 17:01:09 -0700 Kees Cook wrote:
> While preparing for Clang randstruct support (which duplicated many of
> the warnings the randstruct GCC plugin warned about), one strange one
> remained only for the randstruct GCC plugin. Eliminating this rids
> the plugin of the last exception.
> 
> It seems the plugin is happy to dereference individual members of
> a cross-struct cast, but it is upset about casting to a whole object
> pointer. This only manifests in one place in the kernel, so just replace
> the variable with individual member accesses. There is no change in
> executable instruction output.
> 
> Drop the last exception from the randstruct GCC plugin.
> 
> Cc: "David S. Miller" <davem@...emloft.net>
> Cc: Jakub Kicinski <kuba@...nel.org>
> Cc: Christoph Hellwig <hch@...radead.org>
> Cc: Paolo Abeni <pabeni@...hat.com>
> Cc: Kuniyuki Iwashima <kuniyu@...zon.co.jp>
> Cc: Alexei Starovoitov <ast@...nel.org>
> Cc: Cong Wang <cong.wang@...edance.com>
> Cc: Al Viro <viro@...iv.linux.org.uk>
> Cc: netdev@...r.kernel.org
> Cc: linux-hardening@...r.kernel.org
> Signed-off-by: Kees Cook <keescook@...omium.org>
> ---
> If someone can Ack this, I can carry it in the gcc-plugins tree,
> as I'm trying to remove all its exceptions so I can drop that code.

Acked-by: Jakub Kicinski <kuba@...nel.org>