SIGSEGV when running ssh_channel.exec_command() over different channels

[kucharskim]

SUMMARY

On OpenBSD -current as of 2024-11-06 I have following backtrace from a core dump:

$ egdb -quiet -batch -x commands.txt -e /usr/local/bin/python3.11 -c python3.11.core                                                                                                                                            
[New process 517943]
Core was generated by `python3.11'.
Program terminated with signal SIGSEGV, Segmentation fault.
#0  0x00000f3db85e2818 in __pyx_type_11pylibsshext_7session_Session () from /usr/local/lib/python3.11/site-packages/pylibsshext/session.cpython-311.so
+show version
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+thread apply all bt

Thread 1 (process 517943):
+bt
#0  0x00000f3db85e2818 in __pyx_type_11pylibsshext_7session_Session () from /usr/local/lib/python3.11/site-packages/pylibsshext/session.cpython-311.so
#1  0x00000f3d570a76c4 in ssh_packet_socket_controlflow_callback (code=<optimized out>, userdata=0xf3e0f34c800) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/packet.c:1443
#2  0x00000f3d570b342b in ssh_socket_pollcallback (p=0xf3d74e617e0, fd=3, revents=<optimized out>, v_s=0xf3e0f315230) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/socket.c:386
#3  0x00000f3d570af365 in ssh_poll_ctx_dopoll (ctx=0xf3d74e5a8d0, timeout=<optimized out>) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/poll.c:743
#4  0x00000f3d570b0bb6 in ssh_handle_packets (session=0xf3e0f34c800, timeout=<optimized out>) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/session.c:686
#5  0x00000f3d570b095b in ssh_handle_packets_termination (session=0xf3e0f34c800, timeout=<optimized out>, fct=0xf3d57091560 <ssh_channel_open_termination>, user=0xf3d74e45e70) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/session.c:755
#6  0x00000f3d5708e195 in channel_open (channel=0xf3d74e45e70, type=0xf3d57070c84 "session", window=64000, maxpacket=32768, payload=0x0) at /usr/obj/ports/libssh-0.10.6/libssh-0.10.6/src/channels.c:364
#7  0x00000f3df5faafb9 in __pyx_pf_11pylibsshext_7channel_7Channel___cinit__ (__pyx_v_self=0xf3d7c974cc0, __pyx_v_session=<error reading variable: Cannot access memory at address 0x0>) at /tmp/.tmp-ansible-pylibssh-pep517-6bgc_omf/src/src/pylibsshext/channel.c:4041
#8  __pyx_pw_11pylibsshext_7channel_7Channel_1__cinit__ (__pyx_v_self=0xf3d7c974cc0, __pyx_args=<optimized out>, __pyx_kwds=<optimized out>) at /tmp/.tmp-ansible-pylibssh-pep517-6bgc_omf/src/src/pylibsshext/channel.c:3939
#9  __pyx_tp_new_11pylibsshext_7channel_Channel (t=<optimized out>, a=<optimized out>, k=<optimized out>) at /tmp/.tmp-ansible-pylibssh-pep517-6bgc_omf/src/src/pylibsshext/channel.c:8577
#10 0x00000f3e06729af9 in type_call (type=0xf3df5fb86a8 <__pyx_type_11pylibsshext_7channel_Channel>, args=0xf3d7c927d90, kwds=0x0) at Objects/typeobject.c:1091
#11 0x00000f3e066a4d68 in _PyObject_MakeTpCall (tstate=0xf3e06a019e0 <_PyRuntime+166184>, callable=0xf3df5fb86a8 <__pyx_type_11pylibsshext_7channel_Channel>, args=0x72963ec892a8, nargs=<optimized out>, keywords=0x0) at Objects/call.c:214
#12 0x00000f3db85d4719 in __pyx_pf_11pylibsshext_7session_7Session_30new_channel (__pyx_v_self=0xf3d7c95f240) at /tmp/.tmp-ansible-pylibssh-pep517-6bgc_omf/src/src/pylibsshext/session.c:11379
#13 __pyx_pw_11pylibsshext_7session_7Session_31new_channel (__pyx_v_self=0xf3d7c95f240, __pyx_args=<optimized out>, __pyx_nargs=<optimized out>, __pyx_kwds=<optimized out>) at /tmp/.tmp-ansible-pylibssh-pep517-6bgc_omf/src/src/pylibsshext/session.c:11330
#14 0x00000f3e066a564d in _PyObject_VectorcallTstate (tstate=0xf3e06a019e0 <_PyRuntime+166184>, callable=0xf3dc50cd490, args=<optimized out>, nargsf=<optimized out>, kwnames=<optimized out>) at ./Include/internal/pycore_call.h:92
#15 PyObject_Vectorcall (callable=0xf3dc50cd490, args=0xf3e0f31acb0, nargsf=2097152, kwnames=0xf3db85e2818 <__pyx_type_11pylibsshext_7session_Session>) at Objects/call.c:299
#16 0x00000f3e067be1cd in _PyEval_EvalFrameDefault (tstate=0xf3e06a019e0 <_PyRuntime+166184>, frame=<optimized out>, throwflag=<optimized out>) at Python/ceval.c:7301
#17 0x00000f3e067adb1e in _PyEval_EvalFrame (tstate=0xf3e06a019e0 <_PyRuntime+166184>, frame=0xf3d7b85b020, throwflag=<error reading variable: Cannot access memory at address 0x0>) at ./Include/internal/pycore_ceval.h:73
#18 _PyEval_Vector (tstate=0xf3e06a019e0 <_PyRuntime+166184>, func=0xf3de6329f80, locals=<optimized out>, args=<error reading variable: Cannot access memory at address 0x0>, argcount=<error reading variable: Cannot access memory at address 0x0>, kwnames=<error reading variable: Cannot access memory at address 0x0>) at Python/ceval.c:6434
#19 PyEval_EvalCode (co=<optimized out>, globals=<optimized out>, locals=<optimized out>) at Python/ceval.c:1148
#20 0x00000f3e0681e6e9 in run_eval_code_obj (tstate=0xf3e06a019e0 <_PyRuntime+166184>, co=0xf3dfd2eb000, globals=0xf3de6350400, locals=0xf3de6350400) at Python/pythonrun.c:1741
#21 run_mod (mod=<optimized out>, filename=<optimized out>, globals=0xf3de6350400, locals=0xf3de6350400, flags=<optimized out>, arena=<optimized out>) at Python/pythonrun.c:1762
#22 0x00000f3e0681e1d5 in pyrun_file (fp=0xf3d26a66dd0 <usual>, filename=0xf3d7c91d990, start=<error reading variable: Cannot access memory at address 0x101>, globals=0xf3de6350400, locals=0xf3de6350400, closeit=1, flags=0x72963ec89710) at Python/pythonrun.c:1657
#23 _PyRun_SimpleFileObject (fp=0xf3d26a66dd0 <usual>, filename=0xf3d7c91d990, closeit=1, flags=0x72963ec89710) at Python/pythonrun.c:440
#24 0x00000f3e0681d3b3 in _PyRun_AnyFileObject (fp=0xf3d26a66dd0 <usual>, filename=0xf3d7c91d990, closeit=1, flags=0x72963ec89710) at Python/pythonrun.c:79
#25 0x00000f3e06847172 in pymain_run_file_obj (program_name=0xf3de63505f0, filename=0xf3d7c91d990, skip_source_first_line=0) at Modules/main.c:360
#26 pymain_run_file (config=<optimized out>) at Modules/main.c:379
#27 pymain_run_python (exitcode=<optimized out>) at Modules/main.c:605
#28 Py_RunMain () at Modules/main.c:684
#29 0x00000f3e06848095 in pymain_main (args=0x72963ec89a28) at Modules/main.c:714
#30 0x00000f3e068484bc in Py_BytesMain (argc=<optimized out>, argv=0xf3e0f31acb0) at Modules/main.c:738
#31 0x00000f3b1df6994b in ?? ()
#32 0x00000f3b1df69820 in ?? ()
#33 0x0000000000000000 in ?? ()
+info threads
  Id   Target Id         Frame 
* 1    process 517943    0x00000f3db85e2818 in __pyx_type_11pylibsshext_7session_Session () from /usr/local/lib/python3.11/site-packages/pylibsshext/session.cpython-311.so
+info locals
No symbol table info available.

ISSUE TYPE

• Bug Report

PYLISSH and LIBSSH VERSION

$ python3 version.py
__full_version__='<pylibsshext v1.2.2 with libssh v0.10.6>'
__libssh_version__='0.10.6'
__version__='1.2.2'
__version_info__=(1, 2, 2)

OS / ENVIRONMENT

This is similar bug report to #645

OpenBSD 7.6-current (GENERIC.MP) #417: Wed Nov  6 15:53:38 MST 2024
    [email protected]:/usr/src/sys/arch/amd64/compile/GENERIC.MP

$ pkg_info -qI python libssh py3-ansible-libssh
python-3.11.10p1
libssh-0.10.6p0
py3-ansible-libssh-1.2.2

STEPS TO REPRODUCE

$ cat test2.py                                                                                                                                                                                                                           
#!/usr/bin/env python3

from pylibsshext.errors import LibsshSessionException
from pylibsshext.session import Session

import logging

HOST = "examplemachine1"
USER = "root"
TIMEOUT = 30
PORT = 22

ssh = Session()

#ssh.set_log_level(logging.DEBUG)

try:
    ssh.connect(
        host=HOST,
        user=USER,
        timeout=TIMEOUT,
        port=PORT,
        # proxycommand="ssh -q -W %h:%p ks2",
    )
except LibsshSessionException as ex:
    print(f"Failed to connect to {HOST}:{PORT} over SSH: {ex!s}")

print(f"ssh.is_connected={ssh.is_connected}")


def run_cmd(cmd):
    print(f"Running {cmd}...", flush=True)
    print(f"ssh.is_connected={ssh.is_connected}")
    ssh_channel = ssh.new_channel()
    print(f"ssh_channel={ssh_channel}", flush=True)

    print(f"Executing exec_command()...", flush=True)
    try:
        cmd_resp = ssh_channel.exec_command(cmd)
        print(f"Executing exec_command()... done", flush=True)

        print(f"stdout type: {type(cmd_resp.stdout)}")
        print(f"stdout:\n{cmd_resp.stdout.decode()}\n")
        print(f"stderr type: {type(cmd_resp.stderr)}")
        print(f"stderr:\n{cmd_resp.stderr.decode()}\n")
        print(f"return code: {cmd_resp.returncode}")
    finally:
        print(f"Executing ssh_channel.close()...", flush=True)
        ssh_channel.close()


run_cmd("uptime")
run_cmd("ls")
run_cmd("hostname")

print("Closing connection...", flush=True)
ssh.close()

EXPECTED RESULTS

Execution of below script should work all the time, but it core dumps intermittently.

$ python3 test2.py

ACTUAL RESULTS

$ python3 test2.py
ssh.is_connected=1
Running uptime...
ssh.is_connected=1
ssh_channel=<pylibsshext.channel.Channel object at 0x73606b60b40>
Executing exec_command()...
Executing exec_command()... done
stdout type: <class 'bytes'>
stdout:
 6:17PM  up  4:58, 0 users, load averages: 0.01, 0.02, 0.00


stderr type: <class 'bytes'>
stderr:


return code: 0
Executing ssh_channel.close()...
Running ls...
ssh.is_connected=1
Segmentation fault (core dumped)

[kucharskim]

Execution log with ssh's LogLevel DEBUG3 and Phython's ssh.set_log_level(logging.DEBUG)
test2-output-ansible-libssh-1.2.2-v001.txt

[kucharskim]

This issue was triggered by similar problem from #645