linux-kernel - Re: [PATCH] overflow: Introduce __DEFINE

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Message-ID: <92dc9f5b-cef8-47ff-ba75-a099fa9c6718@intel.com>
Date: Tue, 3 Jun 2025 15:55:35 +0200
From: Alexander Lobakin <aleksander.lobakin@...el.com>
To: Kees Cook <kees@...nel.org>
CC: "Gustavo A. R. Silva" <gustavoars@...nel.org>,
	<linux-hardening@...r.kernel.org>, <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] overflow: Introduce __DEFINE_FLEX for having no
 initializer

From: Kees Cook <kees@...nel.org>
Date: Fri, 30 May 2025 12:13:16 -0700

> While not yet in the tree, there is a proposed patch[1] that was
> depending on the prior behavior of _DEFINE_FLEX, which did not have an
> explicit initializer. Provide this via __DEFINE_FLEX now, which can also
> have attributes applied (e.g. __uninitialized).
> 
> Examples of the resulting initializer behaviors can be seen here:
> https://godbolt.org/z/P7Go8Tr33
> 
> Link: https://lore.kernel.org/netdev/20250520205920.2134829-9-anthony.l.nguyen@intel.com [1]
> Fixes: 47e36ed78406 ("overflow: Fix direct struct member initialization in _DEFINE_FLEX()")
> Signed-off-by: Kees Cook <kees@...nel.org>

Looks great to me, thanks!

Also, double thanks for this hint about using __uninitialized to
mitigate perf hits with automatic stack initialization -- will
definitely help :)

Olek