Bug 1452034 - when the /etc/hosts file has a line longer than 1028 characters getent ahostsv4 and ahostsv6 will stop working.
Summary: when the /etc/hosts file has a line longer than 1028 characters getent ahosts...
Alias: None
Product: Red Hat Enterprise Linux 7
Classification: Red Hat
Component: glibc
Version: 7.3
Hardware: Unspecified
OS: Unspecified
Target Milestone: rc
: ---
Assignee: Florian Weimer
QA Contact: qe-baseos-tools-bugs
Vladimír Slávik
Depends On:
Blocks: 1420851 1452032
TreeView+ depends on / blocked
Reported: 2017-05-18 08:13 UTC by Raul Mahiques
Modified: 2020-12-14 08:41 UTC (History)
11 users (show)

Fixed In Version: glibc-2.17-202.el7
Doc Type: No Doc Update
Doc Text:
Clone Of: 1452032
Last Closed: 2018-04-10 13:58:28 UTC
Target Upstream Version:

Attachments (Terms of Use)

System ID Private Priority Status Summary Last Updated
Red Hat Knowledge Base (Solution) 3047071 0 None None None 2017-05-22 13:48:35 UTC
Red Hat Product Errata RHSA-2018:0805 0 None None None 2018-04-10 14:00:11 UTC
Sourceware 21915 0 P2 RESOLVED nss_files can return with NSS_STATUS_SUCCESS and a clobbered errno value, causing getaddrinfo to fail 2020-12-24 16:13:40 UTC

Description Raul Mahiques 2017-05-18 08:13:19 UTC
+++ This bug was initially created as a clone of Bug #1452032 +++

Description of problem:
when the /etc/hosts file has a line longer than 1028 characters getent ahostsv4 and ahostsv6 will stop working for hostsnames present in /etc/hosts.
This happens even if the line is a comment.

Version-Release number of selected component (if applicable):
Tested in RHEL 6.9 and RHEL 7.3

How reproducible:

Steps to Reproduce:
With this oneliner you can see how it stops resolving after the line reaches 1028 characters, even if it's commented.
echo -n '#' >>/etc/hosts ; for i in $(seq 1 1030); do echo -n "$i - "; echo -n 'a' >>/etc/hosts ; getent ahostsv4 `hostname -f`; done

Actual results:
It stops working after 1028 characters.

Expected results:
It continues working and at least ignores the commented line

Additional info:

--- Additional comment from Red Hat Bugzilla Rules Engine on 2017-05-18 04:12:24 EDT ---

Since this bug report was entered in Red Hat Bugzilla, the release flag has been set to ? to ensure that it is properly evaluated for this release.

Comment 5 Florian Weimer 2017-08-02 18:02:44 UTC
The core issue is that getaddrinfo looks at h_errno even if nss_files returns NSS_STATUS_SUCCESS.  The reproducer triggers an internal failure within nss_files, which overwrites h_errno, although the nss_files succeeds eventually.

Upstream, we will fix this by changing getaddrinfo, but *how* is not completely clear to me yet.

Downstream, we can either rebase getaddrinfo (more or less required to fix bug 168253), or patch nss_files not to leak the temporary h_errno value in this case.

Comment 6 Florian Weimer 2017-08-11 10:52:44 UTC
Upstream patch posted: https://sourceware.org/ml/libc-alpha/2017-08/msg00292.html

Comment 16 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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