Use checked arithmetic for frame header totals - #133
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`FramedProducer::grant` sizes its request as `sz + size_of::<H>()` and `FramedConsumer::read` validates a frame as `size_of::<H>() + hdr <= grant_len`. Both sums are unchecked. `H = u16` cannot overflow either one, but `H = usize` can, and the two failure modes are worse than a rejected grant. On the write side the wrapped total asks the coordinator for a handful of bytes while the returned grant still carries the caller's original `sz` in its header, which is the length `Deref`/`DerefMut` hand to `slice::from_raw_parts`. On the read side the wrap lands under `grant_len` and so satisfies the very check that exists to reject an inconsistent header. Debug builds catch both as an overflow panic; release builds do not.
This was referenced Jul 31, 2026
cf-rhett
marked this pull request as ready for review
July 31, 2026 19:34
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FramedProducer::grantsizes its request assz + size_of::<H>(), andFramedConsumer::readvalidates a frame withsize_of::<H>() + hdr <= grant_len. Both sums are unchecked. WithH = u16neither can overflow; withH = usizeboth can.On the write side, a wrapped total asks the coordinator for a handful of bytes while the returned
FramedGrantWstill carries the caller's originalszinhdr— which is the lengthDeref/DerefMutpass toslice::from_raw_parts. The grant hands out a slice far larger than the allocation it covers.On the read side the wrap lands under
grant_len, satisfying the very check that exists to reject an inconsistent header.FramedGrantR::Derefthen builds a slice from the unwrapped header value.Debug builds catch both as an overflow panic. Release builds do not.
Both call sites already return
Result, so this needs no API change. Two regression tests are included; both fail without the fix.