From: Kees Cook <kees@kernel.org>
To: "Rafael V. Volkmer" <rafael.v.volkmer@gmail.com>
Cc: "Gustavo A . R . Silva" <gustavoars@kernel.org>,
linux-hardening@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 0/2] overflow: extend shift helpers and add size_shl()
Date: Thu, 15 Jan 2026 16:43:46 -0800 [thread overview]
Message-ID: <202601151635.9C323403@keescook> (raw)
In-Reply-To: <20251128033830.331426-1-rafael.v.volkmer@gmail.com>
On Fri, Nov 28, 2025 at 12:38:28AM -0300, Rafael V. Volkmer wrote:
> while experimenting with check_shl_overflow() on an architecture with
> native __int128 support, I noticed that the helper always reports
> overflow as soon as the promoted type of @a/@d is wider than 64 bits,
> even when *@d is actually able to represent the shifted value.
Ah, whoops. Yeah. Can you add some tests for int128 to
lib/tests/overflow_kunit.c (see how check_one_op() uses:
check_ ## op ## _overflow
there's a bunch of type checking in there but nothing uses int128, so
there might be more than just shl?
> On a toolchain and architecture that support __int128, this reports
What's the right way to attempt such testing?
--
Kees Cook
prev parent reply other threads:[~2026-01-16 0:43 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-11-28 3:38 [PATCH 0/2] overflow: extend shift helpers and add size_shl() Rafael V. Volkmer
2025-11-28 3:38 ` [PATCH 1/2] overflow: make check_shl_overflow() 128-bit aware Rafael V. Volkmer
2025-11-28 3:38 ` [PATCH 2/2] overflow: add size_shl() helper for saturated left shifts Rafael V. Volkmer
2026-01-16 0:43 ` Kees Cook [this message]
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