6.8-stable review patch. If anyone has any objections, please let me know.
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From: Laine Taffin Altman alexanderaltman@me.com
commit 49ceae68a0df9a92617a61e9ce8a0efcf6419585 upstream.
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 code 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 Reviewed-by: Benno Lossin benno.lossin@proton.me Link: https://lore.kernel.org/r/CA160A4E-561E-4918-837E-3DCEBA74F808@me.com [ Reformatted the comment slightly. ] Signed-off-by: Miguel Ojeda ojeda@kernel.org Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- rust/kernel/init.rs | 11 +++++++++-- 1 file changed, 9 insertions(+), 2 deletions(-)
--- a/rust/kernel/init.rs +++ b/rust/kernel/init.rs @@ -1292,8 +1292,15 @@ 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, (), + // Note: do not add uninhabited types (such as `!` or `core::convert::Infallible`) to this list; + // creating an instance of an uninhabited type is immediate undefined behavior. For more on + // uninhabited/empty types, consult The Rustonomicon: + // https://doc.rust-lang.org/stable/nomicon/exotic-sizes.html#empty-types. The Rust Reference + // also has information on undefined behavior: + // https://doc.rust-lang.org/stable/reference/behavior-considered-undefined.html. + // + // 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>,