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Fix infinite loop when an event is redacted in a v3 room (#4535)

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Richard van der Hoff 2019-01-31 15:34:17 +00:00 committed by GitHub
parent 35f544410a
commit e707e7b38d
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2 changed files with 33 additions and 5 deletions
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changelog.d/4535.bugfix Normal file
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@ -0,0 +1 @@
Fix infinite loop when an event is redacted in a v3 room

37
synapse/storage/events_worker.py
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@ -161,6 +161,12 @@ class EventsWorkerStore(SQLBaseStore):
log_ctx = LoggingContext.current_context()
log_ctx.record_event_fetch(len(missing_events_ids))
# Note that _enqueue_events is also responsible for turning db rows
# into FrozenEvents (via _get_event_from_row), which involves seeing if
# the events have been redacted, and if so pulling the redaction event out
# of the database to check it.
#
# _enqueue_events is a bit of a rubbish name but naming is hard.
missing_events = yield self._enqueue_events(
missing_events_ids,
allow_rejected=allow_rejected,
@ -179,14 +185,35 @@ class EventsWorkerStore(SQLBaseStore):
# instead.
if not allow_rejected and entry.event.type == EventTypes.Redaction:
if entry.event.internal_metadata.need_to_check_redaction():
orig = yield self.get_event(
entry.event.redacts,
# XXX: we need to avoid calling get_event here.
#
# The problem is that we end up at this point when an event
# which has been redacted is pulled out of the database by
# _enqueue_events, because _enqueue_events needs to check the
# redaction before it can cache the redacted event. So obviously,
# calling get_event to get the redacted event out of the database
# gives us an infinite loop.
#
# For now (quick hack to fix during 0.99 release cycle), we just
# go and fetch the relevant row from the db, but it would be nice
# to think about how we can cache this rather than hit the db
# every time we access a redaction event.
#
# One thought on how to do this:
# 1. split _get_events up so that it is divided into (a) get the
# rawish event from the db/cache, (b) do the redaction/rejection
# filtering
# 2. have _get_event_from_row just call the first half of that
orig_sender = yield self._simple_select_one_onecol(
table="events",
keyvalues={"event_id": entry.event.redacts},
retcol="sender",
allow_none=True,
allow_rejected=True,
get_prev_content=False,
)
expected_domain = get_domain_from_id(entry.event.sender)
if orig and get_domain_from_id(orig.sender) == expected_domain:
if orig_sender and get_domain_from_id(orig_sender) == expected_domain:
# This redaction event is allowed. Mark as not needing a
# recheck.
entry.event.internal_metadata.recheck_redaction = False