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

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Message-ID: <D8GQJQFGKB8C.DZBUZT4IJIM0@proton.me>
Date: Sat, 15 Mar 2025 09:34:42 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Boqun Feng <boqun.feng@...il.com>, 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>, 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 10:54 PM CET, Boqun Feng wrote:
> 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().

Good catch.

> 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.

I think it's fine to do several of the `as` conversions in a single
patch, but splitting off the makefile changes is a good idea.

---
Cheers,
Benno