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IDProjectCategoryView StatusDate SubmittedLast Update
0000902LDMud 3.6Runtimepublic2022-01-11 02:232022-09-19 22:46
Reporterparadox Assigned ToGnomi  
PrioritynormalSeveritycrashReproducibilityalways
Status resolvedResolutionfixed 
PlatformLinuxOSUbuntuOS Version20.04
Fixed in Version3.6.6 
Summary0000902: LDMud 3.6.5 python initialization time object reference crash
DescriptionWith LDMud 3.6.4 with Python support compiled in it was possible to have a `--python-script` argument that used `import ldmud; ldmud.Object("/some/path.c")` to get a reference to an LPC object, even while the early driver initialization is occurring and the master object is not available.

With LDMud 3.6.5 the same Python startup script causes a reliable segfault. In "Steps to Reproduce" I've included a built binary and core dump from a representative segfault.

This appears to be due to a the `current_ob` being `NULL` before master has been initialized. This in turn causes a call to `ldmud_object_create` to use `NULL` as an argument to `ref_object`, causing a panic.

Here is a GDB session with a backtrace:
```
mud@windmill2:~/dunenextnext/ldmud-3.6.5/test$ gdb --args ../src/ldmud -u-1 -E 0 --no-compat -e -N --cleanup-time -1 --reset-time -1 --max-array 0 --max-callouts 0 --max-bytes 0 --max-file 0 -s-1 -sv-1 --hard-malloc-limit unlimited --min-malloc 0 -ru0 -rm0 -rs0 --no-strict-euids --no-wizlist-file --check-refcounts --check-state 2 --access-file none --access-log none -f test --python-script startup.py -Mmaster -mt-python 65432 --debug-file ../log/result.t-python.log
GNU gdb (Ubuntu 9.2-0ubuntu1~20.04) 9.2
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For help, type "help".
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Reading symbols from ../src/ldmud...
warning: File "/home/mud/dunenextnext/ldmud-3.6.5/src/ldmud-gdb.py" auto-loading has been declined by your `auto-load safe-path' set to "$debugdir:$datadir/auto-load".
To enable execution of this file add
    add-auto-load-safe-path /home/mud/dunenextnext/ldmud-3.6.5/src/ldmud-gdb.py
line to your configuration file "/home/mud/.gdbinit".
To completely disable this security protection add
    set auto-load safe-path /
line to your configuration file "/home/mud/.gdbinit".
For more information about this security protection see the
"Auto-loading safe path" section in the GDB manual. E.g., run from the shell:
    info "(gdb)Auto-loading safe path"
(gdb) run
Starting program: /home/mud/dunenextnext/ldmud-3.6.5/src/ldmud -u-1 -E 0 --no-compat -e -N --cleanup-time -1 --reset-time -1 --max-array 0 --max-callouts 0 --max-bytes 0 --max-file 0 -s-1 -sv-1 --hard-malloc-limit unlimited --min-malloc 0 -ru0 -rm0 -rs0 --no-strict-euids --no-wizlist-file --check-refcounts --check-state 2 --access-file none --access-log none -f test --python-script startup.py -Mmaster -mt-python 65432 --debug-file ../log/result.t-python.log
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
2022.01.11 02:10:38 LDMud 3.6.5 (3.6.5-1-gd8f1ef68) (development)
2022.01.11 02:10:38 Seeding PRNG from /dev/urandom.
2022.01.11 02:10:38 TLS: (OpenSSL) x509 keyfile '/home/mud/dunenextnext/certs/privkey.pem', certfile '/home/mud/dunenextnext/certs/fullchain.pem'
2022.01.11 02:10:38 TLS: (OpenSSL) X509 certificate from '/home/mud/dunenextnext/certs/fullchain.pem': B3:99:2B:EC:AD:C2:AE:1C:E6:64:C1:34:97:69:F6:C8:65:63:6F:21
2022.01.11 02:10:38 TLS: (OpenSSL) trusted x509 certificates from '/home/mud/dunenextnext/certs/fullchain.pem'.
2022.01.11 02:10:38 TLS: Importing built-in default DH parameters.
2022.01.11 02:10:38 mySQL 8.0.27

Program received signal SIGSEGV, Segmentation fault.
ldmud_object_create (ob=0x0) at pkg-python.c:2943
2943 self->lpc_object = ref_object(ob, "ldmud_object_create");
(gdb) bt
#0 ldmud_object_create (ob=0x0) at pkg-python.c:2943
0000001 0x000055555565beca in svalue_to_python (svp=0x7fffffffc710) at pkg-python.c:9322
0000002 python_save_contextvar_value (contextvar=0x5555557b9c08 <python_contextvar_current_object>,
    name=0x5555556c9dbd "ldmud.current_object", object=...) at pkg-python.c:9832
0000003 python_save_context () at pkg-python.c:9857
0000004 0x0000555555660fc5 in python_call_hook_object (hook=1, is_external=<optimized out>, ob=0x7ffff6440b80)
    at pkg-python.c:10410
0000005 0x0000555555619b4a in init_object_variables (ob=ob@entry=0x7ffff6440b80, templ=templ@entry=0x0) at object.c:494
0000006 0x000055555566ed22 in load_object (lname=lname@entry=0x7ffff644ad20 "a", create_super=create_super@entry=false,
    depth=depth@entry=0, isMasterObj=isMasterObj@entry=false, chain=chain@entry=0x0) at simulate.c:2236
0000007 0x000055555566c443 in lookfor_object (str=<optimized out>, bLoad=bLoad@entry=true) at simulate.c:2538
0000008 0x0000555555651a25 in ldmud_object_init_getobject (num_arg=num_arg@entry=0, data=data@entry=0x7fffffffcaa0)
    at pkg-python.c:2600
0000009 0x000055555565c0e9 in call_lpc_secure (fun=fun@entry=0x555555651a10 <ldmud_object_init_getobject>,
    num_arg=num_arg@entry=0, data=data@entry=0x7fffffffcaa0) at pkg-python.c:9759
0000010 0x000055555565c59a in ldmud_object_init (self=0x7ffff5de3540, args=<optimized out>, kwds=<optimized out>)
    at pkg-python.c:2632
0000011 0x00007ffff6edd199 in ?? () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
0000012 0x00007ffff6f3cafb in _PyObject_MakeTpCall () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
0000013 0x00007ffff6d08df3 in ?? () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#14 0x00007ffff6d10ef6 in _PyEval_EvalFrameDefault () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#15 0x00007ffff6e5eecb in _PyEval_EvalCodeWithName () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#16 0x00007ffff6e5f252 in PyEval_EvalCodeEx () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#17 0x00007ffff6e5f63f in PyEval_EvalCode () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#18 0x00007ffff6e200dc in ?? () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#19 0x00007ffff6e21a47 in PyRun_SimpleFileExFlags () from /lib/x86_64-linux-gnu/libpython3.8.so.1.0
#20 0x000055555565faf6 in pkg_python_init (prog_name=<optimized out>) at pkg-python.c:9987
#21 0x0000555555571b52 in main (argc=<optimized out>, argv=0x7fffffffe158) at main.c:581
```
Steps To ReproduceYou can download a core and a binary from https://binaryparadox.net/d/3.6.5.pyinit.segfault.tar.gz

It's also very easy to reproduce. Simply add a `.c` file to your lib, and have the Python script you pass to `--python-script` reference it from the top level package init context with `ldmud.Object("/path/to/ob.c")`. This will cause a segfault at game start.

Additional InformationI have a unit test that reproduces the crash as well as a fix to consider. I'll open a PR with both and leave a comment here with the URL in a moment.
TagsNo tags attached.

Activities

paradox

2022-01-11 02:26

reporter   ~0002674

Here's a branch with a unit test that reproduces the crash, and a potential fix to consider: https://github.com/ldmud/ldmud/pull/69

Issue History

Date Modified Username Field Change
2022-01-11 02:23 paradox New Issue
2022-01-11 02:26 paradox Note Added: 0002674
2022-01-11 08:39 Gnomi Assigned To => Gnomi
2022-01-11 08:39 Gnomi Status new => assigned
2022-09-19 22:46 Gnomi Status assigned => resolved
2022-09-19 22:46 Gnomi Resolution open => fixed
2022-09-19 22:46 Gnomi Fixed in Version => 3.6.6