Commit df27cef1 authored by Benno Lossin's avatar Benno Lossin Committed by Miguel Ojeda
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rust: init: fix `Zeroable` implementation for `Option<NonNull<T>>` and `Option<KBox<T>>` 

According to [1], `NonNull<T>` and `#[repr(transparent)]` wrapper types
such as our custom `KBox<T>` have the null pointer optimization only if
`T: Sized`. Thus remove the `Zeroable` implementation for the unsized
case.

Link: https://doc.rust-lang.org/stable/std/option/index.html#representation

 [1]
Reported-by: default avatarAlice Ryhl <aliceryhl@google.com>
Closes: https://lore.kernel.org/rust-for-linux/CAH5fLghL+qzrD8KiCF1V3vf2YcC6aWySzkmaE2Zzrnh1gKj-hw@mail.gmail.com/


Cc: stable@vger.kernel.org # v6.12+ (a custom patch will be needed for 6.6.y)
Fixes: 38cde0bd ("rust: init: add `Zeroable` trait and `init::zeroed` function")
Signed-off-by: default avatarBenno Lossin <benno.lossin@proton.me>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarAndreas Hindborg <a.hindborg@kernel.org>
Link: https://lore.kernel.org/r/20250305132836.2145476-1-benno.lossin@proton.me


[ Added Closes tag and moved up the Reported-by one. - Miguel ]
Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent 374908a1

rust/kernel/init.rs

+4 −7
Original line number Diff line number Diff line
@@ -1418,17 +1418,14 @@ macro_rules! impl_zeroable { 
    // SAFETY: `T: Zeroable` and `UnsafeCell` is `repr(transparent)`.

    {<T: ?Sized + Zeroable>} UnsafeCell<T>,



    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).

    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee:

    // https://doc.rust-lang.org/stable/std/option/index.html#representation).

    Option<NonZeroU8>, Option<NonZeroU16>, Option<NonZeroU32>, Option<NonZeroU64>,

    Option<NonZeroU128>, Option<NonZeroUsize>,

    Option<NonZeroI8>, Option<NonZeroI16>, Option<NonZeroI32>, Option<NonZeroI64>,

    Option<NonZeroI128>, Option<NonZeroIsize>,



    // SAFETY: All zeros is equivalent to `None` (option layout optimization guarantee).

    //

    // In this case we are allowed to use `T: ?Sized`, since all zeros is the `None` variant.

    {<T: ?Sized>} Option<NonNull<T>>,

    {<T: ?Sized>} Option<KBox<T>>,

    {<T>} Option<NonNull<T>>,

    {<T>} Option<KBox<T>>,



    // SAFETY: `null` pointer is valid.

    //