linux-kernel - Re: [PATCH 0/2] rust: usb: add initial USB abstractions

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: <DD1X19KZHSEF.1W9SU66HVJM9V@kernel.org>
Date: Thu, 25 Sep 2025 15:29:25 +0200
From: "Danilo Krummrich" <dakr@...nel.org>
To: "Greg Kroah-Hartman" <gregkh@...uxfoundation.org>
Cc: "Daniel Almeida" <daniel.almeida@...labora.com>, "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>,
 <linux-kernel@...r.kernel.org>, <rust-for-linux@...r.kernel.org>,
 <linux-usb@...r.kernel.org>
Subject: Re: [PATCH 0/2] rust: usb: add initial USB abstractions

On Thu Sep 25, 2025 at 2:52 PM CEST, Greg Kroah-Hartman wrote:
> Yes, this is not a normal way that bindings will probably be merged into
> the tree, but as I consulted deeply with the USB maintainer about this
> topic while eating some good Paris pizza and French wine this week while
> at the Kernel Recipes conference, I think that this deserves an
> exception as they agree this can be merged now and they will be
> responsible for any fallout.[1]

If you rather have it "staging" in-tree that's of course up to you. :)

But, I'd prefer not to expose the incorrect conversion between a
&usb::Interface<Ctx> and a &usb::Device<Ctx> for a full release in Linus' tree.

Besides other implications, this conversation also implies that
&usb::Device<Core> can be derived from &usb::Interface<Core>, which semantically
means that if the USB interface's device lock is held we infer that the device
lock of the USB device is held as well.

I know the code isn't even built, but I don't want people reading the code to
take wrong conclusions from that.

Also, it's dead code anyways, so maybe just apply the following hunk?

Thanks,
Danilo

diff --git a/rust/kernel/usb.rs b/rust/kernel/usb.rs
index 8899e7520b58..9bc3478cf561 100644
--- a/rust/kernel/usb.rs
+++ b/rust/kernel/usb.rs
@@ -340,18 +340,6 @@ fn as_ref(&self) -> &device::Device<Ctx> {
     }
 }

-impl<Ctx: device::DeviceContext> AsRef<Device<Ctx>> for Interface<Ctx> {
-    fn as_ref(&self) -> &Device<Ctx> {
-        // SAFETY: `self.as_raw()` is valid by the type invariants. For a valid interface,
-        // the helper should always return a valid USB device pointer.
-        let usb_dev = unsafe { bindings::interface_to_usbdev(self.as_raw()) };
-
-        // SAFETY: The helper returns a valid interface pointer that shares the
-        // same `DeviceContext`.
-        unsafe { &*(usb_dev.cast()) }
-    }
-}
-
 // SAFETY: Instances of `Interface` are always reference-counted.
 unsafe impl AlwaysRefCounted for Interface {
     fn inc_ref(&self) {