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Fix soundness hole in Ref::into_ref and into_mut (#721)
This commit implements the fix for #716 which will be released as a new version in version trains 0.2, 0.3, 0.4, 0.5, 0.6, and 0.7. See #716 for a description of the soundness hole and an explanation of why this fix is chosen. Unfortunately, due to dtolnay/trybuild#241, there is no way for us to write a UI test that will detect a failure post-monomorphization, which is when the code implemented in this change is designed to fail. I have manually verified that unsound uses of these APIs now fail to compile. Release 0.7.31.
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,118 @@ | ||
| // Copyright 2018 The Fuchsia Authors | ||
| // | ||
| // Licensed under the 2-Clause BSD License <LICENSE-BSD or | ||
| // https://opensource.org/license/bsd-2-clause>, Apache License, Version 2.0 | ||
| // <LICENSE-APACHE or https://www.apache.org/licenses/LICENSE-2.0>, or the MIT | ||
| // license <LICENSE-MIT or https://opensource.org/licenses/MIT>, at your option. | ||
| // This file may not be copied, modified, or distributed except according to | ||
| // those terms. | ||
|
|
||
| //! Code that should fail to compile during the post-monomorphization compiler | ||
| //! pass. | ||
| //! | ||
| //! Due to [a limitation with the `trybuild` crate][trybuild-issue], we cannot | ||
| //! use our UI testing framework to test compilation failures that are | ||
| //! encountered after monomorphization has complated. This module has one item | ||
| //! for each such test we would prefer to have as a UI test, with the code in | ||
| //! question appearing as a rustdoc example which is marked with `compile_fail`. | ||
| //! This has the effect of causing doctests to fail if any of these examples | ||
| //! compile successfully. | ||
| //! | ||
| //! This is very much a hack and not a complete replacement for UI tests - most | ||
| //! notably because this only provides a single "compile vs fail" bit of | ||
| //! information, but does not allow us to depend upon the specific error that | ||
| //! causes compilation to fail. | ||
| //! | ||
| //! [trybuild-issue]: https://github.com/dtolnay/trybuild/issues/241 | ||
|
|
||
| // Miri doesn't detect post-monimorphization failures as compile-time failures, | ||
| // but instead as runtime failures. | ||
| #![cfg(not(miri))] | ||
|
|
||
| /// ```compile_fail | ||
| /// use core::cell::{Ref, RefCell}; | ||
| /// | ||
| /// let refcell = RefCell::new([0u8, 1, 2, 3]); | ||
| /// let core_ref = refcell.borrow(); | ||
| /// let core_ref = Ref::map(core_ref, |bytes| &bytes[..]); | ||
| /// | ||
| /// // `zc_ref` now stores `core_ref` internally. | ||
| /// let zc_ref = zerocopy::Ref::<_, u32>::new(core_ref).unwrap(); | ||
| /// | ||
| /// // This causes `core_ref` to get dropped and synthesizes a Rust | ||
| /// // reference to the memory `core_ref` was pointing at. | ||
| /// let rust_ref = zc_ref.into_ref(); | ||
| /// | ||
| /// // UB!!! This mutates `rust_ref`'s referent while it's alive. | ||
| /// *refcell.borrow_mut() = [0, 0, 0, 0]; | ||
| /// | ||
| /// println!("{}", rust_ref); | ||
| /// ``` | ||
| #[allow(unused)] | ||
| const REFCELL_REF_INTO_REF: () = (); | ||
|
|
||
| /// ```compile_fail | ||
| /// use core::cell::{RefCell, RefMut}; | ||
| /// | ||
| /// let refcell = RefCell::new([0u8, 1, 2, 3]); | ||
| /// let core_ref_mut = refcell.borrow_mut(); | ||
| /// let core_ref_mut = RefMut::map(core_ref_mut, |bytes| &mut bytes[..]); | ||
| /// | ||
| /// // `zc_ref` now stores `core_ref_mut` internally. | ||
| /// let zc_ref = zerocopy::Ref::<_, u32>::new(core_ref_mut).unwrap(); | ||
| /// | ||
| /// // This causes `core_ref_mut` to get dropped and synthesizes a Rust | ||
| /// // reference to the memory `core_ref` was pointing at. | ||
| /// let rust_ref_mut = zc_ref.into_mut(); | ||
| /// | ||
| /// // UB!!! This mutates `rust_ref_mut`'s referent while it's alive. | ||
| /// *refcell.borrow_mut() = [0, 0, 0, 0]; | ||
| /// | ||
| /// println!("{}", rust_ref_mut); | ||
| /// ``` | ||
| #[allow(unused)] | ||
| const REFCELL_REFMUT_INTO_MUT: () = (); | ||
|
|
||
| /// ```compile_fail | ||
| /// use core::cell::{Ref, RefCell}; | ||
| /// | ||
| /// let refcell = RefCell::new([0u8, 1, 2, 3]); | ||
| /// let core_ref = refcell.borrow(); | ||
| /// let core_ref = Ref::map(core_ref, |bytes| &bytes[..]); | ||
| /// | ||
| /// // `zc_ref` now stores `core_ref` internally. | ||
| /// let zc_ref = zerocopy::Ref::<_, [u16]>::new_slice(core_ref).unwrap(); | ||
| /// | ||
| /// // This causes `core_ref` to get dropped and synthesizes a Rust | ||
| /// // reference to the memory `core_ref` was pointing at. | ||
| /// let rust_ref = zc_ref.into_slice(); | ||
| /// | ||
| /// // UB!!! This mutates `rust_ref`'s referent while it's alive. | ||
| /// *refcell.borrow_mut() = [0, 0, 0, 0]; | ||
| /// | ||
| /// println!("{:?}", rust_ref); | ||
| /// ``` | ||
| #[allow(unused)] | ||
| const REFCELL_REFMUT_INTO_SLICE: () = (); | ||
|
|
||
| /// ```compile_fail | ||
| /// use core::cell::{RefCell, RefMut}; | ||
| /// | ||
| /// let refcell = RefCell::new([0u8, 1, 2, 3]); | ||
| /// let core_ref_mut = refcell.borrow_mut(); | ||
| /// let core_ref_mut = RefMut::map(core_ref_mut, |bytes| &mut bytes[..]); | ||
| /// | ||
| /// // `zc_ref` now stores `core_ref_mut` internally. | ||
| /// let zc_ref = zerocopy::Ref::<_, [u16]>::new_slice(core_ref_mut).unwrap(); | ||
| /// | ||
| /// // This causes `core_ref_mut` to get dropped and synthesizes a Rust | ||
| /// // reference to the memory `core_ref` was pointing at. | ||
| /// let rust_ref_mut = zc_ref.into_mut_slice(); | ||
| /// | ||
| /// // UB!!! This mutates `rust_ref_mut`'s referent while it's alive. | ||
| /// *refcell.borrow_mut() = [0, 0, 0, 0]; | ||
| /// | ||
| /// println!("{:?}", rust_ref_mut); | ||
| /// ``` | ||
| #[allow(unused)] | ||
| const REFCELL_REFMUT_INTO_MUT_SLICE: () = (); |
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