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Date: Mon, 28 Sep 2026 16:42:35 -0700
From: Andrew Morton <akpm@linux-foundation.org>
To: Bill Wendling <morbo@google.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>, Alexander Potapenko
 <glider@google.com>, Andrey Konovalov <andreyknvl@gmail.com>, Dmitry Vyukov
 <dvyukov@google.com>, Vincenzo Frascino <vincenzo.frascino@arm.com>, Kees
 Cook <kees@kernel.org>, "Gustavo A. R. Silva" <gustavoars@kernel.org>,
 kasan-dev@googlegroups.com, linux-mm@kvack.org,
 linux-kernel@vger.kernel.org, linux-hardening@vger.kernel.org,
 thomas.weissschuh@linutronix.de
Subject: Re: [PATCH] kasan: add KUnit tests for __counted_by and
 __counted_by_ptr
Message-Id: <20260928164235.041803152d3f340d4c59e59e@linux-foundation.org>
In-Reply-To: <20260928231737.2092716-1-morbo@google.com>
References: <20260928231737.2092716-1-morbo@google.com>
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On Mon, 28 Sep 2026 23:17:37 +0000 Bill Wendling <morbo@google.com> wrote:

> The '__counted_by' and '__counted_by_ptr' attributes associate a
> flexible array member or pointer member with a struct field that holds
> its element count. Supporting compilers use these annotations to
> compute dynamic object sizes via '__builtin_dynamic_object_size()' and
> perform runtime bounds checking with KASAN.
> 
> Add KUnit tests ('counted_by_flex_oob_access' and
> 'counted_by_ptr_oob_access', guarded by CONFIG_CC_HAS_COUNTED_BY and
> CONFIG_CC_HAS_COUNTED_BY_PTR respectively) to verify that:
> 
>  - '__builtin_dynamic_object_size()' returns the expected byte size for
>    annotated flexible array and pointer members.
>  - KASAN detects out-of-bounds read and write accesses beyond the
>    annotated count.
> 
> Allocate the test structures in 'noinline' helpers and hide the
> returned pointers with OPTIMIZER_HIDE_VAR() so allocation-size
> attributes and compiler optimizations do not mask the '__counted_by'
> and '__counted_by_ptr' checks.

Thanks.  Are any of Sashiko's comments pertinent?
	https://sashiko.dev/#/patchset/20260928231737.2092716-1-morbo@google.com