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Date: Wed, 13 Mar 2024 23:09:37 +0000
To: Miguel Ojeda <ojeda@kernel.org>, Alex Gaynor <alex.gaynor@gmail.com>, 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>, Benno Lossin <benno.lossin@proton.me>, Andreas Hindborg <a.hindborg@samsung.com>, Alice Ryhl <aliceryhl@google.com>, Martin Rodriguez Reboredo <yakoyoku@gmail.com>
From: Benno Lossin <benno.lossin@proton.me>
Cc: Laine Taffin Altman <alexanderaltman@me.com>, stable@vger.kernel.org, rust-for-linux@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: [PATCH] rust: init: remove impl Zeroable for Infallible
Message-ID: <20240313230713.987124-1-benno.lossin@proton.me>
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From: Laine Taffin Altman <alexanderaltman@me.com>

It is not enough for a type to be a ZST to guarantee that zeroed memory
is a valid value for it; it must also be inhabited. Creating a value of
an uninhabited type, ZST or no, is immediate UB.
Thus remove the implementation of `Zeroable` for `Infallible`, since
that type is not inhabited.

Cc: stable@vger.kernel.org
Fixes: 38cde0bd7b67 ("rust: init: add `Zeroable` trait and `init::zeroed` f=
unction")
Closes: https://github.com/Rust-for-Linux/pinned-init/pull/13
Signed-off-by: Laine Taffin Altman <alexanderaltman@me.com>
Signed-off-by: Benno Lossin <benno.lossin@proton.me>
---
 rust/kernel/init.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs
index 424257284d16..538e03cfc84a 100644
--- a/rust/kernel/init.rs
+++ b/rust/kernel/init.rs
@@ -1292,8 +1292,8 @@ macro_rules! impl_zeroable {
     i8, i16, i32, i64, i128, isize,
     f32, f64,
=20
-    // SAFETY: These are ZSTs, there is nothing to zero.
-    {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, Infallible,=
 (),
+    // SAFETY: These are inhabited ZSTs, there is nothing to zero and a va=
lid value exists.
+    {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, (),
=20
     // SAFETY: Type is allowed to take any value, including all zeros.
     {<T>} MaybeUninit<T>,

base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
--=20
2.42.0