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Bug 2011220 - bind: race condition in zone reloading causes notify not being always sent
Summary: bind: race condition in zone reloading causes notify not being always sent
Keywords:
Status: CLOSED ERRATA
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: bind
Version: 7.9
Hardware: Unspecified
OS: Unspecified
urgent
medium
Target Milestone: rc
: ---
Assignee: Petr Menšík
QA Contact: Petr Sklenar
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2021-10-06 09:45 UTC by Stepan Broz
Modified: 2021-11-23 17:19 UTC (History)
4 users (show)

Fixed In Version: bind-9.11.4-26.P2.el7_9.8
Doc Type: Bug Fix
Doc Text:
Cause: Some internal flags are checked during loading without proper locking. Results are not reliable and suffer from a race condition. Consequence: Sending notifies after zone load is not always sent to all secondary servers as it should. Fix: Check loading status always when data is locked, ensuring race condition does not exist in multiple worker threads. Result: Zone loading is more reliable and notifies are always sent out.
Clone Of:
Environment:
Last Closed: 2021-11-23 17:15:12 UTC
Target Upstream Version:
Embargoed:

Attachments (Terms of Use)
Patch modified to apply on top of bind-9.11.4-26.P2.el7_9.3 (786 bytes, patch)
2021-10-06 09:45 UTC, Stepan Broz 		no flags Details | Diff
View All


Links
System ID Private Priority Status Summary Last Updated
Internet Systems Consortium (ISC) isc-projects bind9 merge_requests 804 0 None None None 2021-10-14 09:03:15 UTC
Red Hat Issue Tracker RHELPLAN-98969 0 None None None 2021-10-06 09:45:54 UTC
Red Hat Product Errata RHBA-2021:4784 0 None None None 2021-11-23 17:15:13 UTC

Description Stepan Broz 2021-10-06 09:45:38 UTC 
Created attachment 1829777 [details]
Patch modified to apply on top of bind-9.11.4-26.P2.el7_9.3

Description of problem:
When doing a mass update of authoritative zones, the notifies are not always sent to the slave servers causing a delay in synchronization of the DATA across the DNS infrastructure.

Version-Release number of selected component (if applicable):
bind-9.11.4-26.P2.el7_9.3.x86_64

How reproducible:
Hard, at customer site only

Steps to Reproduce:
1. Define ~20 authoritative zones on a multi-processor system (the more CPUs the better)
2. Make sure the zones have a slave defined using "IN NS" resource records.
3. Start named.
4. Increase serial in the SOA for all zones
5. # rndc reload

Actual results:
Reload and the change of serial is detected, but the "sending notifies" line is not always sent for all the changed zones.

This is not always logged for all zones:
"notify: info: zone example001.com/IN: sending notifies (serial 2)"

Expected results:
All slaves are sent a notify.

Additional info:
Fix/Patch: https://gitlab.isc.org/isc-projects/bind9/-/commit/56003e9f9f72c8be67d553f4dbd16eba849ca864?merge_request_iid=795

Customer verified a fix in a test package.

RHEL-8.4 not affected (contains the fix already)
Comment 4 Petr Menšík 2021-10-14 09:16:29 UTC 
The change seems quite safe, no real chance to cause regressions. Change were applied in 9.11.5 [1], it is already part of RHEL8. Especially when tested by the customer already.

1. https://gitlab.isc.org/isc-projects/bind9/commit/74cd632f18758d40cf93bdc64b413234fc911ee3
Comment 14 errata-xmlrpc 2021-11-23 17:15:12 UTC 
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (bind bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2021:4784
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