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Fix LruCache corruption bug with a size_callback that can return 0 #11454

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merged 8 commits into from
Nov 30, 2021
Merged

Fix LruCache corruption bug with a size_callback that can return 0 #11454

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cfae8c9
Fix `LruCache` corruption bug with a `size_callback` that can return 0
Nov 29, 2021
3c86fae
Add questionable unit test
Nov 29, 2021
a136975
Add newsfile
Nov 29, 2021
14e816e
Tweak docstring
Nov 29, 2021
b1a1c9b
Update synapse/util/caches/lrucache.py
squahtx Nov 30, 2021
644c0d0
Merge branch 'develop' into squah/fix_lrucache_corruption
Nov 30, 2021
1971a13
Use sentinel value in `drop_from_cache` check
Nov 30, 2021
6a9dc2d
Update newsfile
Nov 30, 2021
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5 changes: 4 additions & 1 deletion synapse/util/caches/lrucache.py
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Original file line number Diff line number Diff line change
Expand Up @@ -271,7 +271,10 @@ def drop_from_cache(self) -> None:
removed from all lists.
"""
cache = self._cache()
if cache is None or cache.pop(self.key, None) is None:
if (
cache is None
or cache.pop(self.key, _Sentinel.sentinel) is _Sentinel.sentinel
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So that we can store None as a value in the cache?

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That was the thinking, yes.

Although drop_from_lists is idempotent so it's functionally the same

):
# `cache.pop` should call `drop_from_lists()`, unless this Node had
# already been removed from the cache.
self.drop_from_lists()
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