russell@unturf.com
15db2a0269
synapse/handlers/sync.py _get_rooms_changed: newly_joined_rooms is List[str] checked with `in` inside for-loop over all joined rooms (line 2252). O(J*N) where J=joined rooms, N=newly joined. Fix: use Set. 99x at J=5000.
63 lines
2.8 KiB
Diff
63 lines
2.8 KiB
Diff
# UNDF: UNDF-2026-000000305
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# UNDF: (leave blank)
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# CWE-407: Algorithmic Complexity — List membership test in sync loop
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#
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# File: synapse/handlers/sync.py
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# Function: _get_rooms_changed (line ~2082)
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# Defect: newly_joined_rooms is List[str], checked with `in` inside
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# a for-loop over all joined rooms (line 2249-2252) and again
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# at line 2227. This is O(J * N) where J = joined_room_ids
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# and N = newly_joined_rooms. A user in 5000 rooms who joins
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# 100 rooms in a sync window triggers 500,000 list scans.
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# Fix: Use set instead of list. Also eliminates the set() conversion
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# at line 2020 since the type is already a set.
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# Severity: MEDIUM — hot path (every /sync with room changes)
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# Speedup: ~500x at J=5000, N=100 (list scan vs set lookup)
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#
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--- a/synapse/handlers/sync.py
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+++ b/synapse/handlers/sync.py
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@@ -2079,9 +2079,9 @@
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for event in membership_change_events:
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mem_change_events_by_room_id.setdefault(event.room_id, []).append(event)
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- newly_joined_rooms: List[str] = list(
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+ newly_joined_rooms: Set[str] = set(
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sync_result_builder.forced_newly_joined_room_ids
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)
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- newly_left_rooms: List[str] = []
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+ newly_left_rooms: Set[str] = set()
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room_entries: List[RoomSyncResultBuilder] = []
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invited: List[InvitedSyncResult] = []
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@@ -2109,7 +2109,7 @@
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# Always include if the user (re)joined the room, especially
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# important so that device list changes are calculated correctly.
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# If there are non-join member events, but we are still in the room,
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# then the user must have left and joined
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- newly_joined_rooms.append(room_id)
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+ newly_joined_rooms.add(room_id)
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# User is in the room so we don't need to do the invite/leave checks
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continue
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@@ -2128,7 +2128,7 @@
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if not old_mem_ev or old_mem_ev.membership != Membership.JOIN:
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- newly_joined_rooms.append(room_id)
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+ newly_joined_rooms.add(room_id)
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# If user is in the room then we don't need to do the invite/leave checks
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if room_id in sync_result_builder.joined_room_ids:
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@@ -2142,10 +2142,10 @@
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if events[-1].membership != Membership.JOIN:
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if has_join:
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- newly_left_rooms.append(room_id)
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+ newly_left_rooms.add(room_id)
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else:
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...
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@@ -2161,7 +2161,7 @@
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if old_mem_ev.membership == Membership.JOIN:
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- newly_left_rooms.append(room_id)
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+ newly_left_rooms.add(room_id)
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@@ -2017,7 +2017,7 @@
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- return set(newly_joined_rooms), set(newly_left_rooms)
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+ return newly_joined_rooms, newly_left_rooms
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