From: "Alexandre Courbot" <acourbot@nvidia.com>
To: "Younes Akhouayri via B4 Relay" <devnull+git.younes.io@kernel.org>
Cc: git@younes.io, "Yury Norov" <yury.norov@gmail.com>,
"Miguel Ojeda" <ojeda@kernel.org>,
"Boqun Feng" <boqun@kernel.org>, "Gary Guo" <gary@garyguo.net>,
"Björn Roy Baron" <bjorn3_gh@protonmail.com>,
"Benno Lossin" <lossin@kernel.org>,
"Andreas Hindborg" <a.hindborg@kernel.org>,
"Alice Ryhl" <aliceryhl@google.com>,
"Trevor Gross" <tmgross@umich.edu>,
"Danilo Krummrich" <dakr@kernel.org>,
"Daniel Almeida" <daniel.almeida@collabora.com>,
"Tamir Duberstein" <tamird@kernel.org>,
"Onur Özkan" <work@onurozkan.dev>,
rust-for-linux@vger.kernel.org, stable@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] rust: num: restrict bool conversion to unsigned Bounded
Date: Mon, 24 Aug 2026 12:16:09 +0900 [thread overview]
Message-ID: <DKWUJ4D1GOPO.BK9DSJBSWJPJ@nvidia.com> (raw)
In-Reply-To: <20260822-fix-rust-bounded-from-bool-submit-v4-1-aa780bfe7f30@younes.io>
On Sat Aug 22, 2026 at 5:44 PM JST, Younes Akhouayri via B4 Relay wrote:
> From: Younes Akhouayri <git@younes.io>
>
> From<bool> turns true into 1. A signed Bounded with N = 1 can hold
> only -1 and 0. The current implementation can therefore create a value
> that breaks Bounded's invariant. Deref relies on that invariant and
> calls unreachable_unchecked() when it is broken, so safe Rust can reach
> undefined behavior.
>
> The other primitive conversions require the source and destination to
> have the same signedness. Treat bool as an unsigned one-bit value and
> allow conversions between bool and Bounded only when the backing integer
> type is unsigned.
>
> Fixes: 01e345e82ec3 ("rust: num: add Bounded integer wrapping type")
> Closes: https://lore.kernel.org/rust-for-linux/OzuVxu0--J-9@younes.io/
> Cc: stable@vger.kernel.org
> Suggested-by: Alexandre Courbot <acourbot@nvidia.com>
> Assisted-by: Codex:gpt-5.6-sol
> Signed-off-by: Younes Akhouayri <git@younes.io>
Thanks for this fix!
Reviewed-by: Alexandre Courbot <acourbot@nvidia.com>
next prev parent reply other threads:[~2026-08-24 3:16 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-22 8:44 Younes Akhouayri via B4 Relay
2026-08-24 3:16 ` Alexandre Courbot [this message]
2026-08-24 11:32 ` Miguel Ojeda
2026-08-24 15:27 ` Alexandre Courbot
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