linux-kernel - Re: [PATCH v10 5/5] rust: Add OwnableRefCounted and SimpleOwnableRefCounted

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 for Android: free password hash cracker in your pocket

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

Message-ID: <aBn1jJBRToyElrF3@mango>
Date: Tue, 06 May 2025 11:42:08 +0000
From: Oliver Mangold <oliver.mangold@...me>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: 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>, Trevor Gross <tmgross@...ch.edu>, Asahi Lina <lina@...hilina.net>, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v10 5/5] rust: Add OwnableRefCounted and SimpleOwnableRefCounted

On 250502 1143, Alice Ryhl wrote:
> On Fri, May 02, 2025 at 09:03:04AM +0000, Oliver Mangold wrote:
> > +pub unsafe trait SimpleOwnableRefCounted: RefCounted {
> > +    /// Checks if exactly one [`ARef`] to the object exists. In case the object is [`Sync`], the
> > +    /// check needs to be race-free.
> > +    fn is_unique(&self) -> bool;
> > +}
> > +
> > +#[cfg_attr(RUSTC_HAS_DO_NOT_RECOMMEND, diagnostic::do_not_recommend)]
> > +// SAFETY: Safe by the requirements on implementation of [`SimpleOwnableRefCounted`].
> > +unsafe impl<T: SimpleOwnableRefCounted> OwnableRefCounted for T {
> > +    fn try_from_shared(this: ARef<Self>) -> Result<Owned<Self>, ARef<Self>> {
> > +        if T::is_unique(&*this) {
> > +            // SAFETY: Safe by the requirements on implementation of [`SimpleOwnable`].
> > +            Ok(unsafe { Owned::from_raw(ARef::into_raw(this)) })
> > +        } else {
> > +            Err(this)
> > +        }
> > +    }
> > +}
> > +
> > +#[cfg_attr(RUSTC_HAS_DO_NOT_RECOMMEND, diagnostic::do_not_recommend)]
> > +// SAFETY: Safe by the requirements on implementation of [`SimpleOwnableRefCounted`].
> > +unsafe impl<T: SimpleOwnableRefCounted> Ownable for T {
> > +    unsafe fn release(this: NonNull<Self>) {
> > +        // SAFETY: Safe by the requirements on implementation of
> > +        // [`SimpleOwnableRefCounted::dec_ref()`].
> > +        unsafe { RefCounted::dec_ref(this) };
> > +    }
> > +}
> 
> I wonder if this is too limiting. It will limit our ability to write
> other blanket impls for Ownable and OwnableRefCounted. Using e.g. a
> derive macro might be better?
> 
> Alice

You might be right. I don't have a strong opinion on the matter.

I'm not really familiar with procmacros, though. So maybe I should just do
away with SimpleOwnableRefCounted for now?

I mean Andreas doesn't need it for his current use case and this or a derive
macro can always be added later if it makes sense.

Best regards,

Oliver