Bug 1435615 - nscd is not caching ldap netgroup data properly, hangs on nscd -i netgroup
Summary: nscd is not caching ldap netgroup data properly, hangs on nscd -i netgroup
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: glibc
Version: 7.2
Hardware: x86_64
OS: Linux
Target Milestone: rc
: ---
Assignee: DJ Delorie
QA Contact: Sergey Kolosov
Depends On: 1277672
Blocks: 1420851 1473718
TreeView+ depends on / blocked
Reported: 2017-03-24 11:41 UTC by Deepu K S
Modified: 2019-11-14 09:07 UTC (History)
14 users (show)

Fixed In Version: glibc-2.17-201.el7
Doc Type: Bug Fix
Doc Text:
Cause: incorrect use of locks in nscd Consequence: On systems where netgroups are cached by nscd, nscd may occasionally hang, resulting in a failure to notice updates in cached information. Fix: nscd has been patched to properly release its internal locks when handling cache timeouts. Result: Cache data should properly update now.
Clone Of: 1277672
Last Closed: 2018-04-10 13:58:28 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Priority Status Summary Last Updated
Debian BTS 800523 None None None 2017-03-24 11:41:31 UTC
Red Hat Product Errata RHSA-2018:0805 None None None 2018-04-10 14:00:11 UTC
Sourceware 22161 None None None 2019-06-30 13:30:16 UTC

Comment 8 DJ Delorie 2017-09-26 15:56:18 UTC
To reproduce the core of this issue, the following steps must happen:

* Configure a service that nscd can cache, which provides netgroup maps.  I use LDAP but others should work also.
* Ensure it has at least one positive query for "in net group" (which may require other maps)
* Perform multiple identical "in net group" queries within the TTL time.  If the cached service is remote, you can tell when you have enough when network traffic stops.  I used getent netgroup QAUsers "" testuser23461 ""

(the bug has now been triggered; the next steps show the effects)

* wait for the entry to time out (the positive TTL time).
* If you watch the logs (enable debug) you can see the message where the cleanup task tries to purge it, or after the timeout time, you can use "nscd -i netgroup" to force a purge

If you let the cleanup task run, you can attach to nscd with gdb and "info threads" - one will be waiting for a write lock.

If you use "nscd -i netgroup" it will hang.

To "reset" this test, you need to stop nscd *and* manually remove the persistent cached databases it uses.

Comment 13 errata-xmlrpc 2018-04-10 13:58:28 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, and where to find the updated
files, follow the link below.

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


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