[
https://issues.apache.org/jira/browse/ZOOKEEPER-1519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13422447#comment-13422447
]
Stephen Tyree commented on ZOOKEEPER-1519:
------------------------------------------
Duplicating the data wouldn't help in circumstances where the data is a
structure contain malloc'd memory, i.e.:
struct Foo {
const char* bar;
};
> 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
> Environment: Ubuntu 11.10, Ubuntu packaged Zookeeper 3.3.3 with some
> backported fixes.
> Reporter: Mark Gius
>
> 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.
--
This message is automatically generated by JIRA.
If you think it was sent incorrectly, please contact your JIRA administrators:
https://issues.apache.org/jira/secure/ContactAdministrators!default.jspa
For more information on JIRA, see: http://www.atlassian.com/software/jira
