Bug Report from www.isc.org:

Name: Radek Zajic
Email: radek@zajic.v.pytli.cz
Software Version: any, with libraries containing fix for RT #46709
OS: Linux
Subject:isc-dhcp crashes when running in DHCPv6 mode


Bug Detail
===========
As described on https://bugs.launchpad.net/ubuntu/+source/isc-dhcp/+bug/1781699 (and the linked bugs), there is an issue within ISC DHCP. This issue did not directly manifest itself until a bug was fixed in BIND libraries (RT #46709), which are used in ISC DHCP too.
When ISC DHCP is compiled with the respective libraries (https://gitlab.isc.org/wpk/bind9/commit/65a483106e45704e19781bfe4f4634db4f77562e), the server crashes when running in DHCPv6 mode. It appears so that the DHCPv6 code somehow tries to delete a heap entry that has been already deleted. This results in failed assertion in the library code, followed by application backtrace.

In the bug report on Ubuntu site, I have also posted a quick-and-dirty patch. This patch checks the heap index and if it is nonzero, it does not call the isc_heap_delete function. This obviously does not resolve the root cause, only avoids the crashes.

Could you kindly check if this can be fixed - and if yes, provide a patch? Thank you very much.

Kind regards,
Radek Zajic

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