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Segfault after running 'saveconfig' when adding a new user from a python module [$50] #286

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opened 2026-10-05 04:10:10 +02:00 by adam · 4 comments
adam commented 2026-10-05 04:10:10 +02:00
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ZNC 1.2, Ubuntu 12.04

  1. Run the below python module code
  2. From a connected client, run 'saveconfig'

ZNC now segfaults. Backtrace found below

Python module:

username = "testusername"
password = "testpassword"

if (username == "" or password == ""):
    return znc.CONTINUE

self.PutModule("Creating new user")
salt = znc.CUtils.GetSalt()
hash = znc.CUser.SaltedHash(password, salt)

new_user = znc.CUser(username)
new_user.SetPass(hash, znc.CUser.HASH_DEFAULT, salt)

str_err = znc.String()
if (znc.CZNC.Get().AddUser(new_user, str_err) == False):
    self.PutModule("adduser error [" + str_err.s + "]")
    return znc.CONTINUE

self.PutModule("User added [" + new_user.GetUserName() + ", " + new_user.GetPass() + "]")

Backtrace:

Program received signal SIGSEGV, Segmentation fault.
CUser::IsValid (this=0x555556b11c30, sErrMsg=..., bSkipPass=false) at src/User.cpp:836
836     src/User.cpp: No such file or directory.
(gdb) backtrace
#0  CUser::IsValid (this=0x555556b11c30, sErrMsg=..., bSkipPass=false) at src/User.cpp:836
#1  0x00005555555aba71 in CZNC::WriteConfig (this=0x555555893040) at src/znc.cpp:503
#2  0x00005555556449cc in CClient::UserCommand (this=0x555556b215f0, sLine=...) at src/ClientCommand.cpp:156
#3  0x00005555555e738d in CClient::ReadLine (this=0x555556b215f0, sData=...) at src/Client.cpp:337
#4  0x0000555555591cb2 in Csock::PushBuff (this=0x555556b215f0, data=<optimized out>, len=<optimized out>, bStartAtZero=<optimized out>) at src/Csocket.cpp:1986
#5  0x000055555559beb3 in CSocketManager::Loop (this=0x5555558930c8) at src/Csocket.cpp:2894
#6  0x00005555555983ef in CSocketManager::DynamicSelectLoop (this=0x5555558930c8, iLowerBounds=100000, iUpperBounds=600000000, iMaxResolution=<optimized out>)
    at src/Csocket.cpp:2952
#7  0x00005555555b0ef0 in CZNC::Loop (this=0x555555893040) at src/znc.cpp:213
#8  0x0000555555581c0c in main (argc=2, argv=0x7fffffffe158) at src/main.cpp:352

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ZNC 1.2, Ubuntu 12.04 1. Run the below python module code 2. From a connected client, run 'saveconfig' ZNC now segfaults. Backtrace found below Python module: ``` username = "testusername" password = "testpassword" if (username == "" or password == ""): return znc.CONTINUE self.PutModule("Creating new user") salt = znc.CUtils.GetSalt() hash = znc.CUser.SaltedHash(password, salt) new_user = znc.CUser(username) new_user.SetPass(hash, znc.CUser.HASH_DEFAULT, salt) str_err = znc.String() if (znc.CZNC.Get().AddUser(new_user, str_err) == False): self.PutModule("adduser error [" + str_err.s + "]") return znc.CONTINUE self.PutModule("User added [" + new_user.GetUserName() + ", " + new_user.GetPass() + "]") ``` Backtrace: ``` Program received signal SIGSEGV, Segmentation fault. CUser::IsValid (this=0x555556b11c30, sErrMsg=..., bSkipPass=false) at src/User.cpp:836 836 src/User.cpp: No such file or directory. (gdb) backtrace #0 CUser::IsValid (this=0x555556b11c30, sErrMsg=..., bSkipPass=false) at src/User.cpp:836 #1 0x00005555555aba71 in CZNC::WriteConfig (this=0x555555893040) at src/znc.cpp:503 #2 0x00005555556449cc in CClient::UserCommand (this=0x555556b215f0, sLine=...) at src/ClientCommand.cpp:156 #3 0x00005555555e738d in CClient::ReadLine (this=0x555556b215f0, sData=...) at src/Client.cpp:337 #4 0x0000555555591cb2 in Csock::PushBuff (this=0x555556b215f0, data=<optimized out>, len=<optimized out>, bStartAtZero=<optimized out>) at src/Csocket.cpp:1986 #5 0x000055555559beb3 in CSocketManager::Loop (this=0x5555558930c8) at src/Csocket.cpp:2894 #6 0x00005555555983ef in CSocketManager::DynamicSelectLoop (this=0x5555558930c8, iLowerBounds=100000, iUpperBounds=600000000, iMaxResolution=<optimized out>) at src/Csocket.cpp:2952 #7 0x00005555555b0ef0 in CZNC::Loop (this=0x555555893040) at src/znc.cpp:213 #8 0x0000555555581c0c in main (argc=2, argv=0x7fffffffe158) at src/main.cpp:352 ``` ## <bountysource-plugin> --- Did you help close this issue? Go claim the **[$50 bounty](https://www.bountysource.com/issues/1376369-segfault-after-running-saveconfig-when-adding-a-new-user-from-a-python-module?utm_campaign=plugin&utm_content=tracker%2F1759&utm_medium=issues&utm_source=github)** on [Bountysource](https://www.bountysource.com/?utm_campaign=plugin&utm_content=tracker%2F1759&utm_medium=issues&utm_source=github). </bountysource-plugin> <!-- github-sync-id:25507022 -->
adam closed this issue 2026-10-05 04:10:10 +02:00
adam commented 2026-10-05 04:10:11 +02:00
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For future, bt full shows better backtrace
But in this case, as psychon said on channel, the user gets deleted by modpython when last reference to the python new_user object goes away. The workaround is to store array of such added users somewhere in member of module, so that it will always have a python reference to it. But it will still fail, e.g. when module unloads.
The proper fix would be to add a way to modpython to release ownership of an object.

For future, `bt full` shows better backtrace But in this case, as psychon said on channel, the user gets deleted by modpython when last reference to the python `new_user` object goes away. The workaround is to store array of such added users somewhere in member of module, so that it will always have a python reference to it. But it will still fail, e.g. when module unloads. The proper fix would be to add a way to modpython to release ownership of an object. <!-- github-comment-id:32209823 -->
adam commented 2026-10-05 04:10:12 +02:00
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I guess it should have been obvious, but the same effect happens with CIRCNetwork objects and presumably any other object types too.

I guess it should have been obvious, but the same effect happens with CIRCNetwork objects and presumably any other object types too. <!-- github-comment-id:32252950 -->
adam commented 2026-10-05 04:10:13 +02:00
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If you want to release python ownership of a new created object you can set the thisown attribute to 0:

 new_user.thisown = 0

Will prevent SWIG from cleaning up the object and keep it at live.

If you want to release python ownership of a new created object you can set the thisown attribute to 0: ``` new_user.thisown = 0 ``` Will prevent SWIG from cleaning up the object and keep it at live. <!-- github-comment-id:41963762 -->
adam commented 2026-10-05 04:10:13 +02:00
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Was fixed by https://github.com/znc/znc/commit/a66c6164a7c7085e8fc8b9655fead3ac2affad80.

Was fixed by https://github.com/znc/znc/commit/a66c6164a7c7085e8fc8b9655fead3ac2affad80. <!-- github-comment-id:122344592 -->
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Reference: adam/znc#286