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From "ASF GitHub Bot (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (ZOOKEEPER-2890) Local automatic variable is left uninitialized and then freed.
Date Tue, 05 Sep 2017 11:57:00 GMT

    [ https://issues.apache.org/jira/browse/ZOOKEEPER-2890?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16153531#comment-16153531

ASF GitHub Bot commented on ZOOKEEPER-2890:

Github user xoiss commented on the issue:

    Sorry, I wanna propose it not for the master branch -- closed.

> 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
>              Labels: easyfix
>             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()_ by invalid address+.
> The true case: this happens when an active _multi_ request with _create_ sub-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+. The significant condition is that the _create_ request is not a stand-alone
one, but namely a sub-request within the _multi_ request. In this case the _deserialize_response()_
is called recursively (for each sub-request), and when it is called for the _create_ subrequest
(from the nested _deserialize_multi()_) the _failed_ parameter is assigned with false (0),
so the _if (failed)_ condition branches to the _else_ part. Note that in the stand-alone create-request
case this does not occur.
> *I suspect this may happen not only due to call to _zookeeper_close()_ but on reception
of a true multi-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 overall status and empty
or insufficient payload).

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