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From "Eric Yang (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-8207) Docker container launch use popen have risk of shell expansion
Date Fri, 04 May 2018 01:27:00 GMT

    [ https://issues.apache.org/jira/browse/YARN-8207?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16463266#comment-16463266
] 

Eric Yang commented on YARN-8207:
---------------------------------

[~jlowe] Thank you for the review.  A couple comments:

Args is array of strings.  Null terminator is not required for array when we have length of
the array.  Hence, checking length > DOCKER_ARGS_MAX is fine.  Malloc without + 1 for null
terminator for char** is okay.  If someone write a for loop without using index (length) variable
for loop, it could cause problems.  Having said that, I will change the code to:

{code}
struct args {
    int length;
    char *out[DOCKER_ARG_MAX];
};
{code}

This can be easier to figure out the length of the actual array for other developers.  Container-executor
is one time execution per exec.  Args is not reused, hence, the leak is not happening in practice.
 Args is only reused in test cases.  I plan to change reset_args to release the pointed strings
and assign NULL to each pointer rather than freeing the pointers.  free(args); would do the
actual release of the args structure.

With the above change, I will also change get_docker_*_command to leave args in partial state,
and let caller decide to reset_args if return value is not 0.

> Docker container launch use popen have risk of shell expansion
> --------------------------------------------------------------
>
>                 Key: YARN-8207
>                 URL: https://issues.apache.org/jira/browse/YARN-8207
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: yarn-native-services
>    Affects Versions: 3.0.0, 3.1.0, 3.0.1, 3.0.2
>            Reporter: Eric Yang
>            Assignee: Eric Yang
>            Priority: Major
>              Labels: Docker
>         Attachments: YARN-8207.001.patch, YARN-8207.002.patch, YARN-8207.003.patch, YARN-8207.004.patch,
YARN-8207.005.patch
>
>
> Container-executor code utilize a string buffer to construct docker run command, and
pass the string buffer to popen for execution.  Popen spawn a shell to run the command.  Some
arguments for docker run are still vulnerable to shell expansion.  The possible solution is
to convert from char * buffer to string array for execv to avoid shell expansion.



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