Hi,
recently, I have hit to an issue in net-snmp-5.8, that is connected to the bug
report [1].
When I tried to run agentofdeath test from [1], snmpd daemon will crash with
malloc(): smallbin double linked list corrupted or double free() issue and
dumps core (see bellow).
>From log file, I can identified one issue with "Unknown operation".
This issue is in the agentx_got_response function
(agent/mibgroup/agentx/master.c). There isn't implemented action for
NETSNMP_CALLBACK_OP_RESEND (defined in include/net-snmp/library/snmp_api.h).
As result "Unknown operation 6 in agentx_got_response" is shown in log file.
/var/log/messages
-------------------------------
Mar 28 06:52:42 localhost snmpd[12073]: Unknown operation 6 in
agentx_got_response
Mar 28 06:52:43 localhost snmpd[12073]: Unknown operation 6 in
agentx_got_response
Mar 28 06:52:43 localhost snmpd[12073]: malloc(): smallbin double linked list
corrupted
Mar 28 06:52:43 localhost systemd[1]: Started Process Core Dump (PID 13652/UID
0).
Mar 28 06:52:48 localhost systemd[1]: snmpd.service: Main process exited,
code=dumped, status=6/ABRT
Mar 28 06:52:48 localhost systemd[1]: snmpd.service: Failed with result
'core-dump'.
-------------------------------
The "Unknown operation" callback is caused by newly added piece of code in
snmplib/snmp_api.c:
static int
snmp_resend_request(struct session_list *slp, netsnmp_request_list *rp,
int incr_retries)
{
...
tv.tv_sec += tv.tv_usec / 1000000L;
tv.tv_usec %= 1000000L;
rp->expireM = tv;
+ if (rp->callback)
+ rp->callback(NETSNMP_CALLBACK_OP_RESEND, sp,
+ rp->pdu->reqid, rp->pdu, rp->cb_data);
}
return 0;
}
When I tried to remove it, it just stop complaining about operation 6, but the
core dump is still present.
May I ask you for help with this issue? Do you have any idea, what causing this
issue in 5.8 and how to fix it?
I know, that Jan Safranek has fixed this for 5.7 by commit [2], but it looks
like something other has changed and this issue is current again.
[1] https://sourceforge.net/p/net-snmp/bugs/2411/
[2]
https://github.com/net-snmp/net-snmp/commit/793d596838ff7cb48a73b675d62897c56c9e62df
Regards
Josef Ridky
Software Engineer
Core Services Team
Red Hat Czech, s.r.o.
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