linux-kernel - Re: [PATCH 2/8] rust: debugfs: Bind file creation for long-lived Display

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: <CAGSQo01PneAee+C6FijhmW_sJt-H_Br5SfWR3NGWyfwk7vr7sA@mail.gmail.com>
Date: Wed, 30 Apr 2025 08:15:27 -0700
From: Matthew Maurer <mmaurer@...gle.com>
To: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
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>, 
	Alice Ryhl <aliceryhl@...gle.com>, Trevor Gross <tmgross@...ch.edu>, 
	Danilo Krummrich <dakr@...nel.org>, "Rafael J. Wysocki" <rafael@...nel.org>, 
	Sami Tolvanen <samitolvanen@...gle.com>, linux-kernel@...r.kernel.org, 
	rust-for-linux@...r.kernel.org
Subject: Re: [PATCH 2/8] rust: debugfs: Bind file creation for long-lived Display

On Wed, Apr 30, 2025 at 5:06 AM Greg Kroah-Hartman
<gregkh@...uxfoundation.org> wrote:
>
> On Tue, Apr 29, 2025 at 11:15:56PM +0000, Matthew Maurer wrote:
> > Allows creation of files for references that live forever and lack
> > metadata through the `Display` implementation.
>
> What do you mean "live forever"?  There's always a structure somewhere
> that holds it, when it goes away the file/directory should also go away.

That's the builder implementation I mentioned later - it lets you
connect the directory to a resource. This is an initial simpler
version to keep the patches small which lets you export e.g. the
contents of global variables safely.

>
> > The reference must live forever because the corresponding file is
> > reference counted, so there's no way to say the lifetime outlives it
> > otherwise. This restriction will be relaxed later in the series through
> > use of `debugfs_remove`.
>
> Why not use that from the beginning?

Because that requires the builder API + pinning, which I thought would
be a more complex conversation, and wanted to keep the "just register
a file" patch separate from the "here's how you ensure that data lives
at least as long as the debugfs directory" patch.

>
> > The `Display` implementation is used because `seq_printf` needs to route
> > through `%pA`, which in turn routes through Arguments. A more generic
> > API is provided later in the series.
>
> Building stuff up to review only to remove it later makes it harder to
> review :)

It doesn't really get removed - `display_file_raw` is still the
underlying implementation for the more generic API, and this API stays
around as a convenience API.

>
> thanks,
>
> greg k-h