linux-kernel - Re: [PATCH v2] uaccess: rust: use newtype for user pointers

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Message-ID: <0789cbad-3164-4046-b8d6-b245721b6515@kernel.org>
Date: Wed, 28 May 2025 12:52:33 +0200
From: Danilo Krummrich <dakr@...nel.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Alexander Viro
 <viro@...iv.linux.org.uk>, Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
 Arnd Bergmann <arnd@...db.de>, Andrew Morton <akpm@...ux-foundation.org>,
 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>, Trevor Gross <tmgross@...ch.edu>,
 rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2] uaccess: rust: use newtype for user pointers

On 5/27/25 3:53 PM, Alice Ryhl wrote:
> In C code we use sparse with the __user annotation to detect cases where
> a user pointer is mixed up with other things. To replicate that, we
> introduce a new struct UserPtr that serves the same purpose using the
> newtype pattern.
> 
> The UserPtr type is not marked with #[derive(Debug)], which means that
> it's not possible to print values of this type. This avoids ASLR
> leakage.
> 
> The type is added to the prelude as it is a fairly fundamental type
> similar to c_int. The wrapping_add() method is renamed to
> wrapping_byte_add() for consistency with the method name found on raw
> pointers.
> 
> Signed-off-by: Alice Ryhl <aliceryhl@...gle.com>

Reviewed-by: Danilo Krummrich <dakr@...nel.org>