linux-kernel - Re: [PATCH v2] rust: sync: require `T: Sync` for `LockedBy::access`

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: <20240915163622.5f3365fe.gary@garyguo.net>
Date: Sun, 15 Sep 2024 16:36:22 +0100
From: Gary Guo <gary@...yguo.net>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Boqun Feng <boqun.feng@...il.com>, "
 Björn Roy Baron" <bjorn3_gh@...tonmail.com>, Benno Lossin
 <benno.lossin@...ton.me>, Andreas Hindborg <a.hindborg@...sung.com>, Trevor
 Gross <tmgross@...ch.edu>, Martin Rodriguez Reboredo <yakoyoku@...il.com>,
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org,
 stable@...r.kernel.org
Subject: Re: [PATCH v2] rust: sync: require `T: Sync` for `LockedBy::access`

On Sun, 15 Sep 2024 14:41:28 +0000
Alice Ryhl <aliceryhl@...gle.com> wrote:

> The `LockedBy::access` method only requires a shared reference to the
> owner, so if we have shared access to the `LockedBy` from several
> threads at once, then two threads could call `access` in parallel and
> both obtain a shared reference to the inner value. Thus, require that
> `T: Sync` when calling the `access` method.
> 
> An alternative is to require `T: Sync` in the `impl Sync for LockedBy`.
> This patch does not choose that approach as it gives up the ability to
> use `LockedBy` with `!Sync` types, which is okay as long as you only use
> `access_mut`.
> 
> Cc: stable@...r.kernel.org
> Fixes: 7b1f55e3a984 ("rust: sync: introduce `LockedBy`")
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Reviewed-by: Gary Guo <gary@...yguo.net>

You probably also want to have a Suggested-by to credit Boqun for
suggesting the current implementation.

Best,
Gary

> ---
> Changes in v2:
> - Use a `where T: Sync` on `access` instead of changing `impl Sync for
>   LockedBy`.
> - Link to v1: https://lore.kernel.org/r/20240912-locked-by-sync-fix-v1-1-26433cbccbd2@google.com
> ---
>  rust/kernel/sync/locked_by.rs | 18 ++++++++++++++----
>  1 file changed, 14 insertions(+), 4 deletions(-)