linux-kernel - Re: [PATCH v2 5/7] rust: file: add `Kuid` wrapper

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Date:   Wed, 6 Dec 2023 13:57:52 +0100
From:   Alice Ryhl <aliceryhl@...gle.com>
To:     Peter Zijlstra <peterz@...radead.org>
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>,
        Benno Lossin <benno.lossin@...ton.me>,
        Andreas Hindborg <a.hindborg@...sung.com>,
        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 v2 5/7] rust: file: add `Kuid` wrapper

On Wed, Dec 6, 2023 at 1:34 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> On Wed, Dec 06, 2023 at 11:59:50AM +0000, Alice Ryhl wrote:
>
> > diff --git a/rust/helpers.c b/rust/helpers.c
> > index fd633d9db79a..58e3a9dff349 100644
> > --- a/rust/helpers.c
> > +++ b/rust/helpers.c
> > @@ -142,6 +142,51 @@ void rust_helper_put_task_struct(struct task_struct *t)
> >  }
> >  EXPORT_SYMBOL_GPL(rust_helper_put_task_struct);
> >
> > +kuid_t rust_helper_task_uid(struct task_struct *task)
> > +{
> > +     return task_uid(task);
> > +}
> > +EXPORT_SYMBOL_GPL(rust_helper_task_uid);
> > +
> > +kuid_t rust_helper_task_euid(struct task_struct *task)
> > +{
> > +     return task_euid(task);
> > +}
> > +EXPORT_SYMBOL_GPL(rust_helper_task_euid);
>
> So I still object to these on the ground that they're obvious and
> trivial speculation gadgets.
>
> We should not have (exported) functions that are basically a single
> dereference of a pointer argument.
>
> And I do not appreciate my feedback on the previous round being ignored.

I'm sorry about that. I barely know what speculation gadgets are, so I
didn't really know what to respond. But I should have responded by
saying that.

I can reimplement these specific functions as inline Rust functions,
but I don't think I can give you a general solution to the
rust_helper_* problem in this patch series.

Alice