linux-kernel - Re: [PATCH v3 6/6] rust: use strict provenance APIs

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Message-ID: <67d4a57f.c80a0220.16ff45.9cf1@mx.google.com>
Date: Fri, 14 Mar 2025 14:54:03 -0700
From: Boqun Feng <boqun.feng@...il.com>
To: Tamir Duberstein <tamird@...il.com>
Cc: Masahiro Yamada <masahiroy@...nel.org>,
	Nathan Chancellor <nathan@...nel.org>,
	Nicolas Schier <nicolas@...sle.eu>, Miguel Ojeda <ojeda@...nel.org>,
	Alex Gaynor <alex.gaynor@...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>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Brendan Higgins <brendan.higgins@...ux.dev>,
	David Gow <davidgow@...gle.com>, Rae Moar <rmoar@...gle.com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Luis Chamberlain <mcgrof@...nel.org>,
	Russ Weight <russ.weight@...ux.dev>, Rob Herring <robh@...nel.org>,
	Saravana Kannan <saravanak@...gle.com>,	linux-kbuild@...r.kernel.org,
 linux-kernel@...r.kernel.org,	rust-for-linux@...r.kernel.org,
 linux-kselftest@...r.kernel.org,	kunit-dev@...glegroups.com,
 linux-pci@...r.kernel.org,	linux-block@...r.kernel.org,
 devicetree@...r.kernel.org
Subject: Re: [PATCH v3 6/6] rust: use strict provenance APIs

On Fri, Mar 14, 2025 at 08:28:10AM -0400, Tamir Duberstein wrote:
[...]
> --- a/rust/kernel/alloc.rs
> +++ b/rust/kernel/alloc.rs
> @@ -217,7 +217,7 @@ unsafe fn free(ptr: NonNull<u8>, layout: Layout) {
>  
>  /// Returns a properly aligned dangling pointer from the given `layout`.
>  pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull<u8> {
> -    let ptr = layout.align() as *mut u8;
> +    let ptr = crate::with_exposed_provenance_mut(layout.align());

Dangling pointers don't have provenance, neither has its provenance been
exposed. I think should use `without_provenance_mut()` here:

	https://doc.rust-lang.org/std/ptr/fn.without_provenance_mut.html

see also the source of core::ptr::dangling().

The rest Rust code changes look good to me. Although I would suggest you
to split this patch into several patches: you can do the conversion from
"as" pattern to provenance API one file by one file, and this make it
easier for people to review. And after the conversions are done, you can
introduce the Makefile changes.

Regards,
Boqun

[...]