linux-kernel - Re: [PATCH v6] rust: transmute: Add methods for FromBytes trait

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: <CABm2a9eEaKWEtzVkc=ErRCXA3MCMG9S+9+ZU0111S7gcfimf+Q@mail.gmail.com>
Date: Mon, 14 Apr 2025 16:54:16 -0300
From: Christian <christiansantoslima21@...il.com>
To: Matthew Maurer <mmaurer@...gle.com>
Cc: rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org, 
	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>, 
	Benno Lossin <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...nel.org>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, ~lkcamp/patches@...ts.sr.ht, richard120310@...il.com
Subject: Re: [PATCH v6] rust: transmute: Add methods for FromBytes trait

> Consider factoring this out into a helper function, e.g.
> ```
> fn from_bytes_sized<T: FromBytes + Sized>(bytes: &[u8]) -> Option<&T> {
> ```
> which you can then call in here. If you were not trying to handle
> `?Sized`, we could even put it in the trait default implementation.

What do you think about
```
fn from_bytes(bytes: &[u8]) -> Option<&Self>
where:
     Self: Sized
```
for the default implementation?

> > +                if bytes.len() == core::mem::size_of::<$t>() {
> > +                    let slice_ptr = bytes.as_ptr().cast::<$t>();
>
> There's no alignment check, and so the resulting constructed reference
> may be misaligned, which is UB. Same below.

I see, I didn't think about it. Good catch and thanks for the tip!