Fix Reference Count Overflow (Use-After-Free) in Atom::clone#301
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matteoldani wants to merge 1 commit into
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Fix Reference Count Overflow (Use-After-Free) in Atom::clone#301matteoldani wants to merge 1 commit into
matteoldani wants to merge 1 commit into
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Previously, cloning a dynamic Atom blindly incremented the atomic reference count using `fetch_add` without any bounds checking. This allowed a degenerate program to clone an Atom ~2.1 billion times on a 32-bit platform, wrapping the reference count to negative and eventually back to 0. This would cause the entry to be freed while clones still exist, triggering an exploitable Use-After-Free. This patch adds an overflow check to abort the process if the reference count reaches `isize::MAX`, mirroring the safety mechanisms of `std::sync::Arc`. Local benchmarks show the performance impact is less than 0.2 nanoseconds per clone, which is statistically indistinguishable from the baseline noise.
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This PR adds a safeguard against Reference Count Overflow in
Atom::clone.If an
Atom's reference count exceedsisize::MAX, it will now deterministically abort the process (std::process::abort()) rather than wrapping around to a negative number and risking a subsequent Use-After-Free vulnerability.Despite being unlikely to occur in practice, the fix should be easy and without real tradeoffs.
Fixes #299