linux-kernel - Re: [PATCH v7 7/7] rust: enable `clippy::ref_as

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 for Android: free password hash cracker in your pocket

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <D8POWLFKWABG.37BVXN2QCL8MP@proton.me>
Date: Tue, 25 Mar 2025 22:11:27 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Tamir Duberstein <tamird@...il.com>, 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>, Boqun Feng <boqun.feng@...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>, Abdiel Janulgue <abdiel.janulgue@...il.com>, Daniel Almeida <daniel.almeida@...labora.com>, Robin Murphy
	<robin.murphy@....com>, Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>, Maxime Ripard <mripard@...nel.org>, Thomas Zimmermann <tzimmermann@...e.de>, David Airlie <airlied@...il.com>, Simona Vetter <simona@...ll.ch>, FUJITA Tomonori <fujita.tomonori@...il.com>
Cc: 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, dri-devel@...ts.freedesktop.org, netdev@...r.kernel.org
Subject: Re: [PATCH v7 7/7] rust: enable `clippy::ref_as_ptr` lint

On Tue Mar 25, 2025 at 9:07 PM CET, Tamir Duberstein wrote:
> diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
> index 40034f77fc2f..6233af50bab7 100644
> --- a/rust/kernel/str.rs
> +++ b/rust/kernel/str.rs
> @@ -29,7 +29,7 @@ pub const fn is_empty(&self) -> bool {
>      #[inline]
>      pub const fn from_bytes(bytes: &[u8]) -> &Self {
>          // SAFETY: `BStr` is transparent to `[u8]`.
> -        unsafe { &*(bytes as *const [u8] as *const BStr) }
> +        unsafe { &*(core::mem::transmute::<*const [u8], *const Self>(bytes)) }

Hmm I'm not sure about using `transmute` here. Yes the types are
transparent, but I don't think that we should use it here.

>      }
>  
>      /// Strip a prefix from `self`. Delegates to [`slice::strip_prefix`].
> @@ -290,7 +290,7 @@ pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError
>      #[inline]
>      pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
>          // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
> -        unsafe { &mut *(bytes as *mut [u8] as *mut CStr) }
> +        unsafe { &mut *(core::mem::transmute::<*mut [u8], *mut Self>(bytes)) }
>      }
>  
>      /// Returns a C pointer to the string.
> diff --git a/rust/kernel/uaccess.rs b/rust/kernel/uaccess.rs
> index 80a9782b1c6e..c042b1fe499e 100644
> --- a/rust/kernel/uaccess.rs
> +++ b/rust/kernel/uaccess.rs
> @@ -242,7 +242,7 @@ pub fn read_raw(&mut self, out: &mut [MaybeUninit<u8>]) -> Result {
>      pub fn read_slice(&mut self, out: &mut [u8]) -> Result {
>          // SAFETY: The types are compatible and `read_raw` doesn't write uninitialized bytes to
>          // `out`.
> -        let out = unsafe { &mut *(out as *mut [u8] as *mut [MaybeUninit<u8>]) };
> +        let out = unsafe { &mut *(core::mem::transmute::<*mut [u8], *mut [MaybeUninit<u8>]>(out)) };

I have a patch that adds a `cast_slice_mut` method that could be used
here, so I can fix it in that series. But let's not use `transmute` here
either.

---
Cheers,
Benno

>          self.read_raw(out)
>      }
>