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References: <CA160A4E-561E-4918-837E-3DCEBA74F808@me.com>
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From: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
Date: Thu, 4 Apr 2024 13:07:15 +0200
Message-ID: <CANiq72mz3qDrNQgKRPPAdZ8Gndn0W6VSggu0B8e0erNbxyL4YA@mail.gmail.com>
Subject: Re: [PATCH v4] rust: init: remove impl Zeroable for Infallible
To: Laine Taffin Altman <alexanderaltman@me.com>
Cc: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>, 
	Benno Lossin <benno.lossin@proton.me>, rust-for-linux@vger.kernel.org, 
	Wedson Almeida Filho <wedsonaf@gmail.com>, Boqun Feng <boqun.feng@gmail.com>, Gary Guo <gary@garyguo.net>, 
	=?UTF-8?Q?Bj=C3=B6rn_Roy_Baron?= <bjorn3_gh@protonmail.com>, 
	Andreas Hindborg <a.hindborg@samsung.com>, Alice Ryhl <aliceryhl@google.com>, 
	Martin Rodriguez Reboredo <yakoyoku@gmail.com>, lkml <linux-kernel@vger.kernel.org>, 
	stable@vger.kernel.org
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On Wed, Apr 3, 2024 at 11:07=E2=80=AFPM Laine Taffin Altman
<alexanderaltman@me.com> wrote:
>
> In Rust, producing an invalid value of any type is immediate undefined
> behavior (UB); this includes via zeroing memory.  Therefore, since an
> uninhabited type has no valid values, producing any values at all for it =
is
> UB.
>
> The Rust standard library type `core::convert::Infallible` is uninhabited=
,
> by virtue of having been declared as an enum with no cases, which always
> produces uninhabited types in Rust.
>
> The current kernel code allows this UB to be triggered, for example by co=
de
> like `Box::<core::convert::Infallible>::init(kernel::init::zeroed())`.
>
> Thus, remove the implementation of `Zeroable` for `Infallible`, thereby
> avoiding the unsoundness (potential for future UB).
>
> Cc: stable@vger.kernel.org
> Fixes: 38cde0bd7b67 ("rust: init: add `Zeroable` trait and `init::zeroed`=
 function")
> Closes: https://github.com/Rust-for-Linux/pinned-init/pull/13
> Signed-off-by: Laine Taffin Altman <alexanderaltman@me.com>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Reviewed-by: Boqun Feng <boqun.feng@gmail.com>

[ Reformatted the comment slightly. ]

Applied to `rust-fixes` -- thanks everyone! Please feel free to still send =
tags.

Cheers,
Miguel