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Subject: memory leak in _libssh2_channel_open

memory leak in _libssh2_channel_open

From: Steven Dake <sdake_at_redhat.com>
Date: Thu, 23 Feb 2012 19:57:10 -0700

Hi,

I have a long running program which essentially opens a ssh session then
periodically runs an exec operation over the session in a new channel.
I have implemented it as a non-blocking implementation. I am using 1.4.0.

The code seems to work well but I notice there is a bit of a leak found
by valgrind:
==6656== at 0x4A074CD: malloc (vg_replace_malloc.c:236)^M
==6656== by 0x4EAC420: _libssh2_transport_read (transport.c:458)^M
==6656== by 0x4EA0694: _libssh2_packet_requirev (packet.c:1219)^M
==6656== by 0x4E97526: _libssh2_channel_open (channel.c:233)^M
==6656== by 0x4E97A8C: libssh2_channel_open_ex (channel.c:352)^M
==6656== by 0x405C9F: assembly_ssh_exec (trans_ssh.c:116)^M
==6656== by 0x4C3754A: job_dispatch (loop_job.c:39)^M
==6656== by 0x4C35FA6: qb_loop_run (loop.c:45)^M
==6656== by 0x4034DB: main (caped.c:163)^M

If I run my application for 8 hours, the leak adds up to 300k of memory
consumed. I had a look into the code for several hours and don't see an
immediate way to fix the problem. I'm not sure even what the problem
is, as the channel should free all packets on libssh2_channel_free.

The code that implements the exec operation is here:
https://github.com/pacemaker-cloud/pacemaker-cloud/blob/master/src/trans_ssh.c

line 102.

Is my state machine for executing an exec operation incorrect, or is
there a bug in libssh2 here that is known?

Regards
-steve

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Received on 2012-02-24

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