linux-kernel - Re: [PATCH v2 1/8] rust: transmute: add `from_bytes

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Message-Id: <DCC5RO5OQV3D.1I9HSU3SFE46Y@kernel.org>
Date: Tue, 26 Aug 2025 08:50:44 +0200
From: "Benno Lossin" <lossin@...nel.org>
To: "Alexandre Courbot" <acourbot@...dia.com>, "Miguel Ojeda"
 <ojeda@...nel.org>, "Alex Gaynor" <alex.gaynor@...il.com>, "Boqun Feng"
 <boqun.feng@...il.com>, "Gary Guo" <gary@...yguo.net>,
 Björn Roy Baron <bjorn3_gh@...tonmail.com>, "Andreas
 Hindborg" <a.hindborg@...nel.org>, "Alice Ryhl" <aliceryhl@...gle.com>,
 "Trevor Gross" <tmgross@...ch.edu>, "Danilo Krummrich" <dakr@...nel.org>,
 "David Airlie" <airlied@...il.com>, "Simona Vetter" <simona@...ll.ch>,
 "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>, "Maxime Ripard"
 <mripard@...nel.org>, "Thomas Zimmermann" <tzimmermann@...e.de>
Cc: "John Hubbard" <jhubbard@...dia.com>, "Alistair Popple"
 <apopple@...dia.com>, "Joel Fernandes" <joelagnelf@...dia.com>, "Timur
 Tabi" <ttabi@...dia.com>, <rust-for-linux@...r.kernel.org>,
 <linux-kernel@...r.kernel.org>, <nouveau@...ts.freedesktop.org>,
 <dri-devel@...ts.freedesktop.org>
Subject: Re: [PATCH v2 1/8] rust: transmute: add `from_bytes_copy` method to
 `FromBytes` trait

On Tue Aug 26, 2025 at 6:07 AM CEST, Alexandre Courbot wrote:
> `FromBytes::from_bytes` comes with a few practical limitations:
>
> - It requires the bytes slice to have the same alignment as the returned
>   type, which might not be guaranteed in the case of a byte stream,
> - It returns a reference, requiring the returned type to implement
>   `Clone` if one wants to keep the value for longer than the lifetime of
>   the slice.

I think that any `Sized` type that can implement `FromBytes` also can
implement `Copy`, so I don't feel like the last point is a strong one.
But the unaligned byte stream is motivation enough :)

> To overcome these when needed, add a `from_bytes_copy` with a default
> implementation in the trait. `from_bytes_copy` returns an owned value
> that is populated using an unaligned read, removing the lifetime
> constraint and making it usable even on non-aligned byte slices.
>
> Reviewed-by: Alice Ryhl <aliceryhl@...gle.com>
> Signed-off-by: Alexandre Courbot <acourbot@...dia.com>

Reviewed-by: Benno Lossin <lossin@...nel.org>

---
Cheers,
Benno

> ---
>  rust/kernel/transmute.rs | 17 +++++++++++++++++
>  1 file changed, 17 insertions(+)