Two defects in the §9.3 quota path, both invisible to the hermetic suite:
- Audit #4's TOCTOU was real and documented: QuotaCheck and ClaimServer were
separate statements, so two concurrent claims by one user for two different
ownerless servers both read count < max_servers and both won. The gate now
lives inside ClaimServer, in the SAME transaction as the ownership write,
under pg_advisory_xact_lock(hashtext(user_id)) — the aggregate read, the
four-dimension re-check (shared with QuotaCheck via one helper so the two
cannot drift), and the UPDATE are one serialized decision. The loser gets
ErrQuotaExceeded, which both claim handlers map to the same 403 the
sequential path gives; the server row is additionally taken FOR UPDATE so
same-server races still resolve to exactly one winner.
- The server PATCH path called UpdateServerResources(..., 0) for storage even
though a resources patch cannot change storage. The cached columns are the
ONLY input to the quota aggregate, so every resource patch silently dropped
that server's storage contribution from its owner's cap. The handler now
reads the current spec and passes storage through.
Red-then-green: the new pgint test drives two real concurrent claims against
max_servers=1 (before: both win; now: exactly one win + one gated 403, and the
DB shows one owned row); the hermetic suite pins the 403 mapping and the
storage-preserving cache write.
Lemon-miaow
bb68fefe04