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https://issues.apache.org/jira/browse/ZOOKEEPER-1519?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Patrick Hunt updated ZOOKEEPER-1519:
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Fix Version/s: 3.4.6
3.5.0
> Zookeeper Async calls can reference free()'d memory
> ---------------------------------------------------
>
> Key: ZOOKEEPER-1519
> URL: https://issues.apache.org/jira/browse/ZOOKEEPER-1519
> Project: ZooKeeper
> Issue Type: Bug
> Components: c client
> Affects Versions: 3.3.3, 3.3.6
> Environment: Ubuntu 11.10, Ubuntu packaged Zookeeper 3.3.3 with some
> backported fixes.
> Reporter: Mark Gius
> Assignee: Daniel Lescohier
> Fix For: 3.5.0, 3.4.6
>
> Attachments: zookeeper-1519.patch
>
>
> zoo_acreate() and zoo_aset() take a char * argument for data and prepare a
> call to zookeeper. This char * doesn't seem to be duplicated at any point,
> making it possible that the caller of the asynchronous function might
> potentially free() the char * argument before the zookeeper library completes
> its request. This is unlikely to present a real problem unless the freed
> memory is re-used before zookeeper consumes it. I've been unable to
> reproduce this issue using pure C as a result.
> However, ZKPython is a whole different story. Consider this snippet:
> ok = zookeeper.acreate(handle, path, json.dumps(value),
> acl, flags, callback)
> assert ok == zookeeper.OK
> In this snippet, json.dumps() allocates a string which is passed into the
> acreate(). When acreate() returns, the zookeeper request has been
> constructed with a pointer to the string allocated by json.dumps(). Also
> when acreate() returns, that string is now referenced by 0 things (ZKPython
> doesn't bump the refcount) and the string is eligible for garbage collection
> and re-use. The Zookeeper request now has a pointer to dangerous freed
> memory.
> I've been seeing odd behavior in our development environments for some time
> now, where it appeared as though two separate JSON payloads had been joined
> together. Python has been allocating a new JSON string in the middle of the
> old string that an incomplete zookeeper async call had not yet processed.
> I am not sure if this is a behavior that should be documented, or if the C
> binding implementation needs to be updated to create copies of the data
> payload provided for aset and acreate.
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