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| author | Damian Johnson <atagar@torproject.org> | 2019-05-08 11:05:15 -0700 |
|---|---|---|
| committer | Damian Johnson <atagar@torproject.org> | 2019-05-08 11:09:51 -0700 |
| commit | 87cea952a27b024981e70efacc09253e22a7658f (patch) | |
| tree | 854b68f578a6492af26847203f069defaecac2d6 | |
| parent | 80647b6a64551ba725da8433da90e263741a707a (diff) | |
Fix ExitPolicy thread safety bug
Interesting catch from juga! I don't have a repro for the stacktrace they cite,
but the only way our input_rules could potentially be None is if two threads
attempt to parse the input_rules at the same time.
Creating a local reference for the input_rules to avoid this while remaining
lock-free...
https://trac.torproject.org/projects/tor/ticket/29899
| -rw-r--r-- | docs/change_log.rst | 1 | ||||
| -rw-r--r-- | stem/exit_policy.py | 13 |
2 files changed, 10 insertions, 4 deletions
diff --git a/docs/change_log.rst b/docs/change_log.rst index 44153d55..cdb9e450 100644 --- a/docs/change_log.rst +++ b/docs/change_log.rst @@ -51,6 +51,7 @@ The following are only available within Stem's `git repository * Added :func:`~stem.control.Controller.get_uptime` method to the :class:`~stem.control.Controller` * Controller events could fail to be delivered in a timely fashion (:trac:`27173`) * Adjusted :func:`~stem.control.Controller.get_microdescriptors` fallback to also use '.new' cache files (:trac:`28508`) + * ExitPolicies could raise TypeError when read concurrently (:trac:`29899`) * **DORMANT** and **ACTIVE** :data:`~stem.Signal` (:spec:`4421149`) * **Descriptors** diff --git a/stem/exit_policy.py b/stem/exit_policy.py index f02ec146..5bdadf9b 100644 --- a/stem/exit_policy.py +++ b/stem/exit_policy.py @@ -452,14 +452,19 @@ class ExitPolicy(object): return ExitPolicy(*[rule for rule in self._get_rules() if not rule.is_default()]) def _get_rules(self): - if self._rules is None: + # Local reference to our input_rules so this can be lock free. Otherwise + # another thread might unset our input_rules while processing them. + + input_rules = self._input_rules + + if self._rules is None and input_rules is not None: rules = [] is_all_accept, is_all_reject = True, True - if isinstance(self._input_rules, bytes): - decompressed_rules = zlib.decompress(self._input_rules).split(b',') + if isinstance(input_rules, bytes): + decompressed_rules = zlib.decompress(input_rules).split(b',') else: - decompressed_rules = self._input_rules + decompressed_rules = input_rules for rule in decompressed_rules: if isinstance(rule, bytes): |