[asterisk-bugs] [JIRA] (ASTERISK-24287) Race conditons and other problems in res_config_pgsql

[Etienne Lessard (JIRA)]

Etienne Lessard created ASTERISK-24287:
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             Summary: Race conditons and other problems in res_config_pgsql
                 Key: ASTERISK-24287
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-24287
             Project: Asterisk
          Issue Type: Bug
      Security Level: None
    Affects Versions: 11.12.0
            Reporter: Etienne Lessard


While looking to fix a deadlock in res_config_pgsql, I found that there was quite a few problems with the module. Here's what I found:

In the find_table function, if database is NULL and the table is not found in the cache, than the lock on the psql_tables list is not released. An easy way to produce such a deadlock is to call the command "realtime show psql cache foobar" from the CLI; if your database doesn't have a table named "foobar", then the next thread which will try to acquire the psql_tables lock will deadlock.

The find_table function sometimes calls the pgsql_exec function, but it doesn't lock the pgsql_lock mutex before, and the find_table function is not always called with the pgsql_lock mutex locked.  This can cause a range of undefined behaviour if other threads are executing in res_config_pgsql, ranging from crash to deadlock. I've personally observed both.

The command "realtime show pgsql status" use the pgsql connection without obtaining the lock first.

The ESCAPE_STRING macro reference the pgsql connection, but once again, the lock is not systematically acquired before the macro is used, so this can lead to undefined behaviour.

I also found other, less critical problems.

I know the res_config_psql module is an "extended support" module. I would have liked to provide a patch to fix the numerous problems, but didn't have the time, and I instead made the switch to res_config_odbc. That said, I've still decided to open this bug, to let other people know that there's quite a few issues with the module.



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