Skip to content

deliberate UB: OOB access #544

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
merged 1 commit into from
Nov 6, 2024
Merged

deliberate UB: OOB access #544

Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
6 changes: 6 additions & 0 deletions resources/deliberate-ub.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,12 @@ We should evaluate whether there truly is some use-case here that is not current
There is a bunch of code out there that violates these rules one way or another.
All of these are resolved by [Tree Borrows](https://perso.crans.org/vanille/treebor/), though [some subtleties around `as_mut_ptr` do remain](https://github.com/rust-lang/unsafe-code-guidelines/issues/450).

### Other cases

* `gxhash` wants to do a vector-sized load that may go out-of-bounds, and didn't find a better solution than causing UB with an OOB load and then masking off the extra bytes.
See [here](https://github.com/ogxd/gxhash/issues/82) for some discussion and [here](https://github.com/ogxd/gxhash/blob/9eb19b021ff94a7b37beb5f479880d07e029b933/src/gxhash/platform/mod.rs#L18) for the relevant code.
The same [also happens in `compiler-builtins`](https://github.com/rust-lang/compiler-builtins/issues/559).

## Former cases of deliberate UB that have at least a work-in-progress solution to them

* Various `offset_of` implementations caused UB by using `mem::uninitialized()`, or they used `&(*base).field` or `addr_of!((*base).field)` to project a dummy pointer to the field which is UB due to out-of-bounds pointer arithmetic.
Expand Down
Loading