On 03.04.24 23:06, Laine Taffin Altman wrote: > 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@xxxxxxxxxxxxxxx > 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@xxxxxx> > Reviewed-by: Alice Ryhl <aliceryhl@xxxxxxxxxx> > Reviewed-by: Boqun Feng <boqun.feng@xxxxxxxxx> Reviewed-by: Benno Lossin <benno.lossin@xxxxxxxxx> > --- > V3 -> V4: Address review nits; run checkpatch properly. > V2 -> V3: Email formatting correction. > V1 -> V2: Added more documentation to the comment, with links; also added more details to the commit message. > > rust/kernel/init.rs | 11 +++++++++-- > 1 file changed, 9 insertions(+), 2 deletions(-) > > diff --git a/rust/kernel/init.rs b/rust/kernel/init.rs > index 424257284d16..3859c7ff81b7 100644 > --- a/rust/kernel/init.rs > +++ b/rust/kernel/init.rs > @@ -1292,8 +1292,15 @@ 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, (), > + // 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>, > > base-commit: c85af715cac0a951eea97393378e84bb49384734 I don't see this commit in the kernel tree, what did you specify as `--base` when running `git format`? -- Cheers, Benno