linux-kernel - Re: [PATCH] Partially revert "rust: drm: gem: Implement AlwaysRefCounted for all gem objects automatically"

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

Message-Id: <DBKJYLF9E3TY.IM6UZFA0BW9I@kernel.org>
Date: Thu, 24 Jul 2025 22:03:24 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Lyude Paul" <lyude@...hat.com>
Cc: <nouveau@...ts.freedesktop.org>, <dri-devel@...ts.freedesktop.org>,
 <rust-for-linux@...r.kernel.org>, "Daniel Almeida"
 <daniel.almeida@...labora.com>, "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>, "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"
 <lossin@...nel.org>, "Andreas Hindborg" <a.hindborg@...nel.org>, "Alice
 Ryhl" <aliceryhl@...gle.com>, "Trevor Gross" <tmgross@...ch.edu>, "Asahi
 Lina" <lina+kernel@...hilina.net>, "Alyssa Rosenzweig"
 <alyssa@...enzweig.io>, "open list" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] Partially revert "rust: drm: gem: Implement
 AlwaysRefCounted for all gem objects automatically"

On Thu Jul 24, 2025 at 9:15 PM CEST, Lyude Paul wrote:
> -// SAFETY: All gem objects are refcounted.
> -unsafe impl<T: IntoGEMObject> AlwaysRefCounted for T {
> -    fn inc_ref(&self) {
> -        // SAFETY: The existence of a shared reference guarantees that the refcount is non-zero.
> -        unsafe { bindings::drm_gem_object_get(self.as_raw()) };
> -    }
> -
> -    unsafe fn dec_ref(obj: NonNull<Self>) {
> -        // SAFETY: We either hold the only refcount on `obj`, or one of many - meaning that no one
> -        // else could possibly hold a mutable reference to `obj` and thus this immutable reference
> -        // is safe.
> -        let obj = unsafe { obj.as_ref() }.as_raw();
> -
> -        // SAFETY:
> -        // - The safety requirements guarantee that the refcount is non-zero.
> -        // - We hold no references to `obj` now, making it safe for us to potentially deallocate it.
> -        unsafe { bindings::drm_gem_object_put(obj) };
> -    }
> -}

IIUC, you'll add rust/kernel/drm/gem/shmem.rs with a new type shmem::Object that
implements IntoGEMObject, right?

If this is correct, I think that should work.

Do I miss anything?