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Date: Mon, 4 Mar 2024 07:24:49 -0800
From: Jakub Kicinski <kuba@kernel.org>
To: Alexander Lobakin <aleksander.lobakin@intel.com>
Cc: Eric Dumazet <edumazet@google.com>, Kees Cook <keescook@chromium.org>,
 "David S. Miller" <davem@davemloft.net>, Paolo Abeni <pabeni@redhat.com>,
 Andy Shevchenko <andriy.shevchenko@linux.intel.com>, "Gustavo A. R. Silva"
 <gustavoars@kernel.org>, <netdev@vger.kernel.org>,
 <linux-hardening@vger.kernel.org>, Simon Horman <horms@kernel.org>, "Jiri
 Pirko" <jiri@resnulli.us>, Daniel Borkmann <daniel@iogearbox.net>, Coco Li
 <lixiaoyan@google.com>, Amritha Nambiar <amritha.nambiar@intel.com>,
 <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] netdev: Use flexible array for trailing private bytes
Message-ID: <20240304072449.0c10b397@kernel.org>
In-Reply-To: <ae6b1114-1c71-46f0-82e5-23b9f05df1bf@intel.com>
References: <20240229213018.work.556-kees@kernel.org>
	<20240229225910.79e224cf@kernel.org>
	<CANn89iKeJGvhY0K=kLhhR39NVbaizP2UBk0Vk0r_XCe2XMBZHg@mail.gmail.com>
	<9050bdec-b34a-4133-8ba5-021dfd4b1c75@intel.com>
	<CANn89iLSLPn5PyXNQcA2HO0e5jGYvHKhTh_9_EMmfbTJKZPfbg@mail.gmail.com>
	<77d3f074-8cb6-466b-ab31-a7b0bac659d0@intel.com>
	<20240301093517.428e5b5d@kernel.org>
	<ae6b1114-1c71-46f0-82e5-23b9f05df1bf@intel.com>
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On Mon, 4 Mar 2024 15:32:51 +0100 Alexander Lobakin wrote:
> > 100% I should have linked to the thread that led to Kees's work.
> > Adding directly to net_device would be way better but there's
> > a handful of drivers which embed the struct.  
> 
> I think it's okay to embed a struct with flex array at the end as long
> as it's not used? Or the compiler will say that the flex array is not at
> the end of the structure?

Technically, yes. Practically it ties the lifetime of a refcounted
object to something semi-related with different lifetime rules :(