linux-kernel - Re: [PATCH v5 2/4] uaccess: always export _copy_[from|to]_user with CONFIG

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Message-ID: <202404151605.6EFC791E@keescook>
Date: Mon, 15 Apr 2024 16:05:17 -0700
From: Kees Cook <keescook@...omium.org>
To: Alice Ryhl <aliceryhl@...gle.com>
Cc: Miguel Ojeda <ojeda@...nel.org>, Matthew Wilcox <willy@...radead.org>,
	Al Viro <viro@...iv.linux.org.uk>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Alex Gaynor <alex.gaynor@...il.com>,
	Wedson Almeida Filho <wedsonaf@...il.com>,
	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@...sung.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Arve Hjønnevåg <arve@...roid.com>,
	Todd Kjos <tkjos@...roid.com>, Martijn Coenen <maco@...roid.com>,
	Joel Fernandes <joel@...lfernandes.org>,
	Carlos Llamas <cmllamas@...gle.com>,
	Suren Baghdasaryan <surenb@...gle.com>,
	Arnd Bergmann <arnd@...db.de>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, rust-for-linux@...r.kernel.org,
	Christian Brauner <brauner@...nel.org>
Subject: Re: [PATCH v5 2/4] uaccess: always export _copy_[from|to]_user with
 CONFIG_RUST

On Mon, Apr 15, 2024 at 07:13:54AM +0000, Alice Ryhl wrote:
> From: Arnd Bergmann <arnd@...db.de>
> 
> Rust code needs to be able to access _copy_from_user and _copy_to_user
> so that it can skip the check_copy_size check in cases where the length
> is known at compile-time, mirroring the logic for when C code will skip
> check_copy_size. To do this, we ensure that exported versions of these
> methods are available when CONFIG_RUST is enabled.
> 
> Alice has verified that this patch passes the CONFIG_TEST_USER_COPY test
> on x86 using the Android cuttlefish emulator.
> 
> Signed-off-by: Arnd Bergmann <arnd@...db.de>

Thanks for the updates and the comment on testing. :)

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook