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Date: Thu, 25 Sep 2025 17:00:30 -0700
From: Kees Cook <kees@kernel.org>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: Alejandro Colomar <alx@kernel.org>, linux-kernel@vger.kernel.org,
	Christopher Bazley <chris.bazley.wg14@gmail.com>,
	Rasmus Villemoes <linux@rasmusvillemoes.dk>,
	Marco Elver <elver@google.com>, Michal Hocko <mhocko@suse.com>,
	Linus Torvalds <torvalds@linux-foundation.org>,
	Al Viro <viro@zeniv.linux.org.uk>,
	Alexander Potapenko <glider@google.com>,
	Dmitry Vyukov <dvyukov@google.com>, Jann Horn <jannh@google.com>
Subject: Re: [PATCH v1 0/3] Add ENDOF(), and use it to fix off-by-one bugs
Message-ID: <202509251657.F4ED4CF@keescook>
References: <cover.1758806023.git.alx@kernel.org>
 <20250925134814.1f68d84a951572245893abbe@linux-foundation.org>
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In-Reply-To: <20250925134814.1f68d84a951572245893abbe@linux-foundation.org>

On Thu, Sep 25, 2025 at 01:48:14PM -0700, Andrew Morton wrote:
> Patchset seems reasonable, I guess.  But I'm not loving "ENDOF".  End
> of what - is that like __etext?  "ARRAY_END" matches "ARRAY_SIZE" quite
> nicely, no?  And it much better describes what the thing does.

And it's really ARRAY_BEYOND. ;) I don't really like having APIs that
require holding pointers that are actively invalid, either.

u8 array[10];
u8 *first = array; // valid address
u8 *last = &array[ARRAY_SIZE(array) - 1]; // valid address

for (u8 *c = first; c <= last; c++)
  putc(*c);
// c would now be invalid but has left scope so it cannot be used

-- 
Kees Cook