From a481fb9f98ad10e5e129bdc7664c59498a7332f6 Mon Sep 17 00:00:00 2001 From: Patrick Cloke Date: Fri, 10 Feb 2023 08:09:47 -0500 Subject: [PATCH] Refactor get_user_devices_from_cache to avoid mutating cached values. (#15040) The previous version of the code could mutate a cached value, but only if the input requested all devices of a user *and* a specific device. To avoid this nonsensical situation we no longer fetch a specific device ID if all of a user's devices are returned. --- changelog.d/15040.misc | 1 + synapse/handlers/e2e_keys.py | 11 +++++--- synapse/storage/databases/main/devices.py | 31 +++++++++++++---------- 3 files changed, 25 insertions(+), 18 deletions(-) create mode 100644 changelog.d/15040.misc diff --git a/changelog.d/15040.misc b/changelog.d/15040.misc new file mode 100644 index 000000000..ca129b64a --- /dev/null +++ b/changelog.d/15040.misc @@ -0,0 +1 @@ +Avoid mutating a cached value in `get_user_devices_from_cache`. diff --git a/synapse/handlers/e2e_keys.py b/synapse/handlers/e2e_keys.py index d2188ca08..43cbece21 100644 --- a/synapse/handlers/e2e_keys.py +++ b/synapse/handlers/e2e_keys.py @@ -159,19 +159,22 @@ class E2eKeysHandler: # A map of destination -> user ID -> device IDs. remote_queries_not_in_cache: Dict[str, Dict[str, Iterable[str]]] = {} if remote_queries: - query_list: List[Tuple[str, Optional[str]]] = [] + user_ids = set() + user_and_device_ids: List[Tuple[str, str]] = [] for user_id, device_ids in remote_queries.items(): if device_ids: - query_list.extend( + user_and_device_ids.extend( (user_id, device_id) for device_id in device_ids ) else: - query_list.append((user_id, None)) + user_ids.add(user_id) ( user_ids_not_in_cache, remote_results, - ) = await self.store.get_user_devices_from_cache(query_list) + ) = await self.store.get_user_devices_from_cache( + user_ids, user_and_device_ids + ) # Check that the homeserver still shares a room with all cached users. # Note that this check may be slightly racy when a remote user leaves a diff --git a/synapse/storage/databases/main/devices.py b/synapse/storage/databases/main/devices.py index 766c2052f..85c1778a8 100644 --- a/synapse/storage/databases/main/devices.py +++ b/synapse/storage/databases/main/devices.py @@ -746,42 +746,45 @@ class DeviceWorkerStore(RoomMemberWorkerStore, EndToEndKeyWorkerStore): @trace @cancellable async def get_user_devices_from_cache( - self, query_list: List[Tuple[str, Optional[str]]] + self, user_ids: Set[str], user_and_device_ids: List[Tuple[str, str]] ) -> Tuple[Set[str], Dict[str, Dict[str, JsonDict]]]: """Get the devices (and keys if any) for remote users from the cache. Args: - query_list: List of (user_id, device_ids), if device_ids is - falsey then return all device ids for that user. + user_ids: users which should have all device IDs returned + user_and_device_ids: List of (user_id, device_ids) Returns: A tuple of (user_ids_not_in_cache, results_map), where user_ids_not_in_cache is a set of user_ids and results_map is a mapping of user_id -> device_id -> device_info. """ - user_ids = {user_id for user_id, _ in query_list} - user_map = await self.get_device_list_last_stream_id_for_remotes(list(user_ids)) + unique_user_ids = user_ids | {user_id for user_id, _ in user_and_device_ids} + user_map = await self.get_device_list_last_stream_id_for_remotes( + list(unique_user_ids) + ) # We go and check if any of the users need to have their device lists # resynced. If they do then we remove them from the cached list. users_needing_resync = await self.get_user_ids_requiring_device_list_resync( - user_ids + unique_user_ids ) user_ids_in_cache = { user_id for user_id, stream_id in user_map.items() if stream_id } - users_needing_resync - user_ids_not_in_cache = user_ids - user_ids_in_cache + user_ids_not_in_cache = unique_user_ids - user_ids_in_cache + # First fetch all the users which all devices are to be returned. results: Dict[str, Dict[str, JsonDict]] = {} - for user_id, device_id in query_list: - if user_id not in user_ids_in_cache: - continue - - if device_id: + for user_id in user_ids: + if user_id in user_ids_in_cache: + results[user_id] = await self.get_cached_devices_for_user(user_id) + # Then fetch all device-specific requests, but skip users we've already + # fetched all devices for. + for user_id, device_id in user_and_device_ids: + if user_id in user_ids_in_cache and user_id not in user_ids: device = await self._get_cached_user_device(user_id, device_id) results.setdefault(user_id, {})[device_id] = device - else: - results[user_id] = await self.get_cached_devices_for_user(user_id) set_tag("in_cache", str(results)) set_tag("not_in_cache", str(user_ids_not_in_cache))