Alexander A. Strelets created ZOOKEEPER-2890:
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Summary: Local automatic variable is left uninitialized and then
freed.
Key: ZOOKEEPER-2890
URL: https://issues.apache.org/jira/browse/ZOOKEEPER-2890
Project: ZooKeeper
Issue Type: Bug
Components: c client
Affects Versions: 3.4.10
Environment: Linux ubuntu 4.4.0-87-generic
gcc (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609
https://github.com/apache/zookeeper.git
branch-3.4
Reporter: Alexander A. Strelets
Priority: Critical
Fix For: 3.4.10
Function *_deserialize_response()_*, in _case COMPLETION_STRING_, uses local
automatic variable *_struct CreateResponse res_* which is +left uninitialized+
and passed to the function _deserialize_GetACLResponse()_ and then to
_deallocate_GetACLResponse()_.
The _deserialize_ function, which is called the first, is expected to assign
the _res_ variable with a value from the parsed _struct iarchive *ia_. But, if
_ia_ contains for example insufficient amount of bytes the
_deserialize_String()_ function refuses of assigning a value to _res_, and
_res_ stays uninitialized (the true case is described below). Then, the
_deallocate_ function calls _deallocate_String()_ passing uninitialized _res_
with arguments. If incidentally the memory region in the program stack under
the _res_ was not equal to NULL, the last call +leads to _free()_ for an
invalid address+.
The true case: this happens for example when an active _create_ request (or
create sub-request within the _multi_ request) is completed on call to
_zookeeper_close()_ with the so called "Fake response" which is fabricated by
the function _free_completions()_. Such response includes only the header but
+zero bytes for the body+.
*I suspect this may happen not only due to call to _zookeeper_close()_ but on
reception of a true response from the server* containing insufficient number of
bytes (I'm not sure if it can be a proper response from the server with an
error status and empty payload).
Also *I suspect the same case will take place with different requests, but not
only the _create_*. Indeed, almost all cases in the _deserialize_response()_
shall be verified as soon as they also use uninitialized _res_-s and
_deallocate_ them. Still I have not checked others except the _create_ request
with _COMPLETION_STRING_ response.
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