👾 Havoc: Rate limit double-spend via time-warp race#1870
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In MemoryStore::decide, Instant::now() is called outside the bucket lock. A thread that stalls after capturing `now` but before acquiring the lock can write its earlier timestamp to `last_refill`, overwriting a later timestamp from a thread that executed quickly. By changing `bucket.last_refill = now` to use `std::cmp::max`, we ensure that `last_refill` strictly moves forwards, preventing the bucket from generating spurious tokens due to time running backwards. Co-authored-by: google-labs-jules[bot] <161369871+google-labs-jules[bot]@users.noreply.github.com>
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Code Review
This pull request fixes a time-warp race condition in the rate limiter's MemoryStore by ensuring last_refill is only updated to a later timestamp, and adds corresponding loom tests to model this behavior and test concurrent channel snapshots. The review feedback suggests gating the new integration test module with #[cfg(feature = "ws")] to maintain consistency and avoid compiling an empty module when the feature is disabled.
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| mod chaos_channels_loom; | ||
| #[cfg(feature = "ws")] | ||
| mod chaos_channels_proptest; | ||
| mod chaos_channels_snapshot_loom; |
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To maintain consistency with the other chaos_channels modules in this file, please gate chaos_channels_snapshot_loom with #[cfg(feature = "ws")]. Although the file itself has an inner attribute #![cfg(feature = "ws")], conditionally compiling the module at the declaration level avoids compiling an empty module when the ws feature is disabled.
| mod chaos_channels_snapshot_loom; | |
| #[cfg(feature = "ws")] | |
| mod chaos_channels_snapshot_loom; |
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🧊 The Trigger: Capturing
Instant::now()outside the lock inMemoryStore::decideallows threads to write a stalelast_refilltime into the bucket, moving time backwards.📉 The Stack Trace: N/A
🧪 Reproduction: Run
RUSTFLAGS="--cfg loom_models" LOOM_MAX_PREEMPTIONS=2 RATE_LIMIT_LOOM_SHOW_BUG=1 cargo test -p autumn-web --test loom_models rate_limit_time_warp.😈 Comment: "Time goes forwards, not backwards. Except when I pause your thread."
PR created automatically by Jules for task 15972419132455313770 started by @madmax983