#1388 patch for bug 2923: snmpv3 bulkget errors result in double free core dump

[Sam Tannous]

This is a patch for https://sourceforge.net/p/net-snmp/bugs/2923/ when almost any v3 bulkget
error will cause a core dump of snmpd.

[Bart Van Assche]

This patch has been applied on the v5.8 and master branches. Thanks for the patch!

[Ming Chen]

Hi Bart,

There is a minor bug in this patch - which might be introduced by a typo error.

• if (old_ref->usr_engine_id_length)
• SNMP_FREE(old_ref->usr_engine_id);
• if (old_ref->usr_auth_protocol_length)
• SNMP_FREE(old_ref->usr_auth_protocol);
• if (old_ref->usr_auth_protocol_length)
• SNMP_FREE(old_ref->usr_priv_protocol);

The bold variable usr_auth_protocol_length should be replaced by usr_priv_protocol_length.