1436335 – NSCD not properly caching netgroup

RHEL Engineering is moving the tracking of its product development work on RHEL 6 through RHEL 9 to Red Hat Jira (issues.redhat.com). If you're a Red Hat customer, please continue to file support cases via the Red Hat customer portal. If you're not, please head to the "RHEL project" in Red Hat Jira and file new tickets here. Individual Bugzilla bugs in the statuses "NEW", "ASSIGNED", and "POST" are being migrated throughout September 2023. Bugs of Red Hat partners with an assigned Engineering Partner Manager (EPM) are migrated in late September as per pre-agreed dates. Bugs against components "kernel", "kernel-rt", and "kpatch" are only migrated if still in "NEW" or "ASSIGNED". If you cannot log in to RH Jira, please consult article #7032570. That failing, please send an e-mail to the RH Jira admins at rh-issues@redhat.com to troubleshoot your issue as a user management inquiry. The email creates a ServiceNow ticket with Red Hat. Individual Bugzilla bugs that are migrated will be moved to status "CLOSED", resolution "MIGRATED", and set with "MigratedToJIRA" in "Keywords". The link to the successor Jira issue will be found under "Links", have a little "two-footprint" icon next to it, and direct you to the "RHEL project" in Red Hat Jira (issue links are of type "https://issues.redhat.com/browse/RHEL-XXXX", where "X" is a digit). This same link will be available in a blue banner at the top of the page informing you that that bug has been migrated.

Bug 1436335 - NSCD not properly caching netgroup

Summary: NSCD not properly caching netgroup

Keywords:
Status:	CLOSED WONTFIX
Alias:	None
Product:	Red Hat Enterprise Linux 6
Classification:	Red Hat
Component:	glibc
Sub Component:
Version:	6.8
Hardware:	Unspecified
OS:	Linux
Priority:	unspecified
Severity:	unspecified
Target Milestone:	rc
Target Release:	---
Assignee:	DJ Delorie
QA Contact:	qe-baseos-tools-bugs
Docs Contact:
URL:
Whiteboard:
Depends On:
Blocks:	1461138 1505647
TreeView+	depends on / blocked

Reported:	2017-03-27 16:53 UTC by Al Heisner
Modified:	2017-10-24 04:31 UTC (History)
CC List:	7 users (show)
Fixed In Version:
Doc Type:	If docs needed, set a value
Doc Text:
Clone Of:
Clones:	1505647 (view as bug list)
Environment:
Last Closed:	2017-10-24 04:31:29 UTC
Target Upstream Version:
Embargoed:

Attachments	(Terms of Use)
patch for netgroupcache.c (435 bytes, patch) 2017-03-27 16:53 UTC, Al Heisner	no flags	Details \| Diff
View All

Description Al Heisner 2017-03-27 16:53:47 UTC

Created attachment 1266715 [details]
patch for netgroupcache.c

Description of problem:
NSCD netgroup cache failure. Persistent cache inspection and logs show that setnetgrent() and innetgr() cache separate GETNETGRENT records in the cache. When the entry corresponding to innetgr() expires, on reload the netgroup entry has 0 results and further calls to innetgr always return 0 even if it should return 1. Debugging nscd, I found that innetgr adds the GETNETGRENT record to cache with the group string not null-terminated.

Version-Release number of selected component (if applicable):
glibc-2.12-1.192.el6.x86_64

How reproducible:
always

Steps to Reproduce:
1. set up netgroups provided by ldap / nslcd
2. perform innetgr() with triplet that returns 1
3. wait for nscd debug log to show expire and reload of GETNETGRENT from innetgr()
4. perform innetgr() again, it returns 0

Actual results:
innetgr always returns 0 after GETNETGRENT record from previous innetgr() expires

Expected results:
innetgr should return 1 if entry is in netgroup or 0 if it is not

Additional info:
I've tested attached patch and it seems to work. One cache record exists from both setnetgrent() and innetgr(), and when it exires it reloads without issue. This has a side benefit of fewer type 19 records in nscd cache and fewer ldap lookup.

Comment 4 DJ Delorie 2017-10-24 04:31:29 UTC

Red Hat Enterprise Linux 6 is now in production stage 3, and this means that
only urgent priority bug fixes will be considered for release. In this case
there are several workarounds including disabling netgroup caching, disabling
nscd, or using an alternate caching framework like sssd. Your analysis does
look correct, but we need to review this further. We have cloned this issue
for RHEL7 here 1505647 to continue looking at the fix there. Thank you very
much for the bug report. We have also filed an upstream issue here: 
https://sourceware.org/bugzilla/show_bug.cgi?id=22342

Note You need to log in before you can comment on or make changes to this bug.