oxidecomputer / oxidecomputer/hubris
UB in ping task: pointer passed to read_volatile must not be null
Nobody has claimed this yet.
- Dominant language
- Rust
- Stars
- 3.6k
- Forks
- 239
- Avg merge
- 1d 12h
- Merged PRs (30d)
- 23
Description
This code executes undefined behavior:
https://github.com/oxidecomputer/hubris/blob/8833cc1dcfdbf107369e188a035a38651ba7ab46/task/ping/src/main.rs#L19
The std::ptr module documents:
A null pointer is never valid, not even for accesses of size zero.
And ptr::read_volatile repeats this:
Note that even if T has size 0, the pointer must be non-null and properly aligned.
I think this line should be replaced with inline assembly that does the faulting read.
Contributor guide
First steps
- Read the whole issue, then the project's contributing guide.
- Comment on the issue to say you are picking it up — it saves two people doing the same work.
- Fork the repository and make your change on a branch.
- Open a pull request that references the issue number.
Research direction
Start in task/ping/src/main.rs at line 19 and read the Rust documentation for ptr::read_volatile and the issue's linked context. Replace the null-pointer volatile read with the proposed faulting-read approach, then verify that the ping task builds and retains the intended fault behavior.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- rust
- Domain
- embedded-iot
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Clearly specified
- Newbie friendliness
- 35/100