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 <20240202-alice-file-v4-4-fc9c2080663b@google.com> <aa0f46bc-6bed-4a4e-9dcd-e34cc2563a37@gmail.com>
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From: Alice Ryhl <aliceryhl@google.com>
Date: Thu, 8 Feb 2024 16:07:53 +0100
Message-ID: <CAH5fLgjSr9bbGc02gDdfFAUTyGiR__6K8qZYQNZLRe_E=Cypjw@mail.gmail.com>
Subject: Re: [PATCH v4 4/9] rust: cred: add Rust abstraction for `struct cred`
To: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Cc: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>, 
	Wedson Almeida Filho <wedsonaf@gmail.com>, Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
	=?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
	Benno Lossin <benno.lossin@proton.me>, Andreas Hindborg <a.hindborg@samsung.com>, 
	Peter Zijlstra <peterz@infradead.org>, Alexander Viro <viro@zeniv.linux.org.uk>, 
	Christian Brauner <brauner@kernel.org>, Greg Kroah-Hartman <gregkh@linuxfoundation.org>, 
	=?UTF-8?B?QXJ2ZSBIasO4bm5ldsOlZw==?= <arve@android.com>, 
	Todd Kjos <tkjos@android.com>, Martijn Coenen <maco@android.com>, 
	Joel Fernandes <joel@joelfernandes.org>, Carlos Llamas <cmllamas@google.com>, 
	Suren Baghdasaryan <surenb@google.com>, Dan Williams <dan.j.williams@intel.com>, 
	Kees Cook <keescook@chromium.org>, Matthew Wilcox <willy@infradead.org>, 
	Thomas Gleixner <tglx@linutronix.de>, Daniel Xu <dxu@dxuuu.xyz>, linux-kernel@vger.kernel.org, 
	rust-for-linux@vger.kernel.org, linux-fsdevel@vger.kernel.org
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On Thu, Feb 8, 2024 at 1:35=E2=80=AFAM Martin Rodriguez Reboredo
<yakoyoku@gmail.com> wrote:
>
> On 2/2/24 07:55, Alice Ryhl wrote:
> > From: Wedson Almeida Filho <wedsonaf@gmail.com>
> >
> > Add a wrapper around `struct cred` called `Credential`, and provide
> > functionality to get the `Credential` associated with a `File`.
> >
> > Rust Binder must check the credentials of processes when they attempt t=
o
> > perform various operations, and these checks usually take a
> > `&Credential` as parameter. The security_binder_set_context_mgr functio=
n
> > would be one example. This patch is necessary to access these security_=
*
> > methods from Rust.
> >
> > Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
> > Co-developed-by: Alice Ryhl <aliceryhl@google.com>
> > Signed-off-by: Alice Ryhl <aliceryhl@google.com>
> > ---
> > [...]
> > +    /// Returns the credentials of the task that originally opened the=
 file.
> > +    pub fn cred(&self) -> &Credential {
> > +        // SAFETY: It's okay to read the `f_cred` field without synchr=
onization because `f_cred` is
> > +        // never changed after initialization of the file.
> > +        let ptr =3D unsafe { (*self.as_ptr()).f_cred };
>
>  From what I can see `file.f_cred` is valid from the moment `file` was
> initialized, worth to notice too IMO.

That's what it says?

Alice