6.6-stable review patch. If anyone has any objections, please let me know. ------------------ From: Benno Lossin <benno.lossin@xxxxxxxxx> commit df27cef153603b18a7d094b53cc3d5264ff32797 upstream. 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: Alice Ryhl <aliceryhl@xxxxxxxxxx> Closes: https://lore.kernel.org/rust-for-linux/CAH5fLghL+qzrD8KiCF1V3vf2YcC6aWySzkmaE2Zzrnh1gKj-hw@xxxxxxxxxxxxxx/ Cc: stable@xxxxxxxxxxxxxxx # v6.12+ (a custom patch will be needed for 6.6.y) Fixes: 38cde0bd7b67 ("rust: init: add `Zeroable` trait and `init::zeroed` function") Signed-off-by: Benno Lossin <benno.lossin@xxxxxxxxx> Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> Reviewed-by: Andreas Hindborg <a.hindborg@xxxxxxxxxx> Link: https://lore.kernel.org/r/20250305132836.2145476-1-benno.lossin@xxxxxxxxx [ Added Closes tag and moved up the Reported-by one. - Miguel ] Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- rust/kernel/init.rs | 11 ++++------- 1 file changed, 4 insertions(+), 7 deletions(-) --- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -1310,17 +1310,14 @@ 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<Box<T>>, + {<T>} Option<NonNull<T>>, + {<T>} Option<Box<T>>, // SAFETY: `null` pointer is valid. //
