linux-kernel - Re: [PATCH v3 2/9] rust: cred: add Rust abstraction for `struct cred`

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Date: Fri, 19 Jan 2024 10:52:15 +0100
From: Alice Ryhl <aliceryhl@...gle.com>
To: Benno Lossin <benno.lossin@...ton.me>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alex Gaynor <alex.gaynor@...il.com>, 
	Wedson Almeida Filho <wedsonaf@...il.com>, Boqun Feng <boqun.feng@...il.com>, Gary Guo <gary@...yguo.net>, 
	Björn Roy Baron <bjorn3_gh@...tonmail.com>, 
	Andreas Hindborg <a.hindborg@...sung.com>, Peter Zijlstra <peterz@...radead.org>, 
	Alexander Viro <viro@...iv.linux.org.uk>, Christian Brauner <brauner@...nel.org>, 
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Arve Hjønnevåg <arve@...roid.com>, 
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>, 
	Joel Fernandes <joel@...lfernandes.org>, Carlos Llamas <cmllamas@...gle.com>, 
	Suren Baghdasaryan <surenb@...gle.com>, Dan Williams <dan.j.williams@...el.com>, 
	Kees Cook <keescook@...omium.org>, Matthew Wilcox <willy@...radead.org>, 
	Thomas Gleixner <tglx@...utronix.de>, Daniel Xu <dxu@...uu.xyz>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org, linux-fsdevel@...r.kernel.org
Subject: Re: [PATCH v3 2/9] rust: cred: add Rust abstraction for `struct cred`

On Fri, Jan 19, 2024 at 10:37 AM Benno Lossin <benno.lossin@...ton.me> wrote:
> On 1/18/24 15:36, Alice Ryhl wrote:
> > +    /// Returns the effective UID of the given credential.
> > +    pub fn euid(&self) -> bindings::kuid_t {
> > +        // SAFETY: By the type invariant, we know that `self.0` is valid.
>
> Is `euid` an immutable property, or why does this memory access not race
> with something?

Yes. These properties are changed by replacing the credential, so the
credentials themselves are immutable.

Alice