Bug 10540

Summary:	getaddrinfo() fails if /etc/hosts is missing, instead of falling through to nss_dns
Product:	glibc	Reporter:	Steve Langasek <vorlon>
Component:	network	Assignee:	Ulrich Drepper <drepper.fsp>
Status:	RESOLVED FIXED
Severity:	normal	CC:	glibc-bugs
Priority:	P2	Flags:	fweimer: security-
Version:	2.10
Target Milestone:	---
Host:	x86_64-linux-gnu	Target:	x86_64-linux-gnu
Build:	x86_64-linux-gnu	Last reconfirmed:
Attachments:	test case patch to nss_files fixing getaddrinfo when /etc/hosts is absent

Description Steve Langasek 2009-08-20 12:30:35 UTC

glibc 2.10 introduces a regression in getaddrinfo(); with a standard nsswitch.conf:

$ grep host /etc/nsswitch.conf 
hosts:          files dns
$

and no /etc/hosts file on the system (which is legitimate; e.g., in a chroot):

$ cat /etc/hosts
cat: /etc/hosts: No such file or directory
$

all calls to getaddrinfo() will fail, short-circuited by an nss_files failure
before invoking nss_dns.

Trivial test case, patch to follow.

Comment 1 Steve Langasek 2009-08-20 12:32:19 UTC

Created attachment 4142 [details]
test case

Comment 2 Steve Langasek 2009-08-20 12:34:32 UTC

Created attachment 4143 [details]
patch to nss_files fixing getaddrinfo when /etc/hosts is absent

Comment 3 Ulrich Drepper 2009-10-30 05:05:33 UTC

I applied the patch.

Comment 4 Michel Hermier 2009-12-19 13:28:52 UTC

Seems the fix is incorrect, on 2.11 I get:

bash-4.0# gcc bug-408901.c
bash-4.0# ./a.out www.redhat.com
www.redhat.com -5
bash-4.0# touch /etc/hosts
bash-4.0# ./a.out www.redhat.com
www.redhat.com 0

It seems that returning NO_DATA (in the patch) stops the host search
prematurely. Instead returning HOST_NOT_FOUND fix the issue, and sounds more
logical.

Comment 5 Andreas Schwab 2013-02-04 15:49:34 UTC

Appears to be working fine with 2.17.