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Fix soundness issue with container_of! macro #474

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Merged
merged 1 commit into from
Jul 31, 2021
Merged

Fix soundness issue with container_of! macro #474

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7 changes: 4 additions & 3 deletions rust/kernel/lib.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -197,7 +197,8 @@ macro_rules! offset_of {
/// # Safety
///
/// Callers must ensure that the pointer to the field is in fact a pointer to the specified field,
/// as opposed to a pointer to another object of the same type.
/// as opposed to a pointer to another object of the same type. If this condition is not met,
/// any dereference of the resulting pointer is UB.
///
/// # Example
///
Expand All @@ -212,7 +213,7 @@ macro_rules! offset_of {
/// fn test() {
/// let test = Test { a: 10, b: 20 };
/// let b_ptr = &test.b;
/// let test_alias = unsafe { container_of!(b_ptr, Test, b) };
/// let test_alias = container_of!(b_ptr, Test, b);
/// // This prints `true`.
/// pr_info!("{}\n", core::ptr::eq(&test, test_alias));
/// }
Expand All @@ -222,6 +223,6 @@ macro_rules! container_of {
($ptr:expr, $type:ty, $($f:tt)*) => {{
let ptr = $ptr as *const _ as *const u8;
let offset = $crate::offset_of!($type, $($f)*);
unsafe { ptr.offset(-offset) as *const $type }
ptr.wrapping_offset(-offset) as *const $type
}}
}