Commit 92fd540d authored by Benno Lossin's avatar Benno Lossin Committed by Miguel Ojeda
Browse files

rust: init: make initializer values inaccessible after initializing 



Previously the init macros would create a local variable with the name
and hygiene of the field that is being initialized to store the value of
the field. This would override any user defined variables. For example:
```
struct Foo {
    a: usize,
    b: usize,
}
let a = 10;
let foo = init!(Foo{
    a: a + 1, // This creates a local variable named `a`.
    b: a, // This refers to that variable!
});
let foo = Box::init!(foo)?;
assert_eq!(foo.a, 11);
assert_eq!(foo.b, 11);
```

This patch changes this behavior, so the above code would panic at the
last assertion, since `b` would have value 10.

Reviewed-by: default avatarMartin Rodriguez Reboredo <yakoyoku@gmail.com>
Reviewed-by: default avatarAlice Ryhl <aliceryhl@google.com>
Reviewed-by: default avatarGary Guo <gary@garyguo.net>
Signed-off-by: default avatarBenno Lossin <benno.lossin@proton.me>
Link: https://lore.kernel.org/r/20230814084602.25699-7-benno.lossin@proton.me


Signed-off-by: default avatarMiguel Ojeda <ojeda@kernel.org>
parent b9b88be0

rust/kernel/init/macros.rs

+11 −9
Original line number Diff line number Diff line
@@ -1075,13 +1075,13 @@ macro_rules! __init_internal { 
        // In-place initialization syntax.

        @munch_fields($field:ident <- $val:expr, $($rest:tt)*),

    ) => {

        let $field = $val;

        let init = $val;

        // Call the initializer.

        //

        // SAFETY: `slot` is valid, because we are inside of an initializer closure, we

        // return when an error/panic occurs.

        // We also use the `data` to require the correct trait (`Init` or `PinInit`) for `$field`.

        unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), $field)? };

        unsafe { $data.$field(::core::ptr::addr_of_mut!((*$slot).$field), init)? };

        // Create the drop guard:

        //

        // We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1107,12 +1107,12 @@ macro_rules! __init_internal { 
        // In-place initialization syntax.

        @munch_fields($field:ident <- $val:expr, $($rest:tt)*),

    ) => {

        let $field = $val;

        let init = $val;

        // Call the initializer.

        //

        // SAFETY: `slot` is valid, because we are inside of an initializer closure, we

        // return when an error/panic occurs.

        unsafe { $crate::init::Init::__init($field, ::core::ptr::addr_of_mut!((*$slot).$field))? };

        unsafe { $crate::init::Init::__init(init, ::core::ptr::addr_of_mut!((*$slot).$field))? };

        // Create the drop guard:

        //

        // We rely on macro hygiene to make it impossible for users to access this local variable.
@@ -1138,11 +1138,13 @@ macro_rules! __init_internal { 
        // Init by-value.

        @munch_fields($field:ident $(: $val:expr)?, $($rest:tt)*),

    ) => {

        {

            $(let $field = $val;)?

            // Initialize the field.

            //

            // SAFETY: The memory at `slot` is uninitialized.

            unsafe { ::core::ptr::write(::core::ptr::addr_of_mut!((*$slot).$field), $field) };

        }

        // Create the drop guard:

        //

        // We rely on macro hygiene to make it impossible for users to access this local variable.