linux-kernel - [PATCH] rust: init: remove impl Zeroable for Infallible

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Date: Wed, 13 Mar 2024 23:09:37 +0000
From: Benno Lossin <benno.lossin@...ton.me>
To: Miguel Ojeda <ojeda@...nel.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>, Alice Ryhl <aliceryhl@...gle.com>, Martin Rodriguez Reboredo <yakoyoku@...il.com>
Cc: Laine Taffin Altman <alexanderaltman@...com>, stable@...r.kernel.org, rust-for-linux@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] rust: init: remove impl Zeroable for Infallible

From: Laine Taffin Altman <alexanderaltman@...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@...r.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@...com>
Signed-off-by: Benno Lossin <benno.lossin@...ton.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,
 
-    // 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 valid value exists.
+    {<T: ?Sized>} PhantomData<T>, core::marker::PhantomPinned, (),
 
     // SAFETY: Type is allowed to take any value, including all zeros.
     {<T>} MaybeUninit<T>,

base-commit: 768409cff6cc89fe1194da880537a09857b6e4db
-- 
2.42.0