Aborting during configuration loading

[ihrwein]

I found a nasty bug in the configuration loading process.

It can be reproduced by following these steps:

1. start syslog-ng with the following (valid) configuration:

   @version: 3.8
   @include "scl.conf"
   
   log {
   source {
     file("/tmp/a.txt");
   };
   destination {
     file("/tmp/a.txt");
   };
   };
   

2. Replace the configuration with the following one:

   @version: 3.8
   @include "scl.conf"
   
   log {
   source {
     # syntactically valid, but semantically invalid -> init() returns FALSE
     file("/tmp/a.txt" multi-line-prefix("a"));
   };
   destination {
     file("/tmp/a.txt");
     };
   };
   

3. Reload syslog-ng

   sbin/syslog-ng-ctl reload
   

Expected result:

[2016-05-26T15:29:21.460108] multi-line-prefix() and/or multi-line-garbage() specified but multi-line-mode() is not regexp based (prefix-garbage or prefix-suffix), please set multi-line-mode() properly;
[2016-05-26T15:29:21.460116] Error initializing message pipeline;
[2016-05-26T15:29:21.460123] Error initializing new configuration, reverting to old config;
[2016-05-26T15:29:21.460157] Unable to detect fully qualified hostname for localhost, use_fqdn() will use the short hostname;
[2016-05-26T15:29:21.460168] Compiling #unnamed sequence [log] at [/home/btibi/work/impl-deinit-for-native-parser/install/etc/syslog-ng.conf:15:2]
[2016-05-26T15:29:21.460176]   Compiling #anon-source0 sequence [source] at [/home/btibi/work/impl-deinit-for-native-parser/install/etc/syslog-ng.conf:15:2]
[2016-05-26T15:29:21.460183]     Compiling #unnamed junction [log] at [/home/btibi/work/impl-deinit-for-native-parser/install/etc/syslog-ng.conf:15:10]
[2016-05-26T15:29:21.460191]       Compiling #unnamed single [log] at [/home/btibi/work/impl-deinit-for-native-parser/install/etc/syslog-ng.conf:17:3]
[2016-05-26T15:29:21.460200] Error cloning pipe into its reference point, probably the element in question is not meant to be used in this situation; location='/home/btibi/work/impl-deinit-for-native-par$er/install/etc/syslog-ng.conf:17:3'
Quit (core dumped)

This problem can be reproduced with plugins whose init() method can return FALSE. affile and the "native" parsers are certainly affected. They are needed to trigger a config reverting.

We need an other plugin which cannot be cloned/clone() could fail. File destinations cannot be cloned, so they are perfect for this purpose.

What happens during the reproduction?

1. original configuration is loaded, everything is fine
   1. PIF_INLINED flag is set on the LogPipe instances
2. we replace the configuration
3. syslog-ng is reloaded
   1. new configuration is created
   2. old configuration is deinitialized
   3. PIF_INLINED flag is still set on the LogPipe instance
   4. new configuration is initialized
      • it will fail, because the configuration is invalid
   5. new configuration is deinitialized
   6. old configuration is initialized
      • as PIF_INLINED is set, we try to clone the pipe -> it will fail https://github.com/balabit/syslog-ng/blob/master/lib/cfg-tree.c#L461-L474
   7. we return with FALSE which will trigger a kill() call https://github.com/balabit/syslog-ng/blob/master/lib/mainloop.c#L217-L223

syslog-ng 3.8 is certainly affected and by looking at the code 3.6 and 3.7 as well.