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Bug#248271: marked as done (nscd freezes when used with libnss-ldap on busy server.)

Your message dated Fri, 05 Aug 2005 19:15:42 +0900
with message-id <[🔎] 81psssu1td.wl%gotom@debian.or.jp>
and subject line Close bugs tagged as woody
has caused the attached Bug report to be marked as done.

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Received: (at submit) by bugs.debian.org; 10 May 2004 08:22:18 +0000
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Date: Mon, 10 May 2004 10:22:14 +0200
To: submit@bugs.debian.org
Subject: nscd freezes when used with libnss-ldap on busy server.
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Subject: nscd freezes when used with libnss-ldap on busy server.
Package: nscd
Version: N/A; reported 2004-05-10
Severity: critical
Justification: breaks the whole system

IMHO what I describe here is a bug in nscd when using 
I've seen some old bug reports on debian and redhat 
with similar problems and some suggestions to not 
use nscd and libnss-ldap together.

We have a mail (postfix 2.1.0) server using debian 
Woody (all security updates made), kernel 2.4.26 
(but had the same problem with kernel 2.4.25).

We use libnss-ldap with local slapd server
(a replication of our primary ldap server)
for users' accounts.


test: ~$head -3 /etc/nsswitch.conf 
passwd: 	ldap files
group: 		ldap files
shadow: 	ldap files


test: ~$cat /etc/libnss-ldap.conf 
base ....
ldap_version 3

The problem is that, using nscd for password caching 
(default configuration) everything works fine, 
but the machine sometimes hangs.

Tests on another test-server have shown that
it can happen (randomly) when postfix has to deliver mail
to aliases with many (more than 100) local users.

The server then hangs (no connection possible even locally) 
but, if we were already logged, we can see the following behaviour:

Everything is fine with the exception of name resolving.
No respons from ls -l or ps -ef or any program
that needs accounts information.

test: ~$strace ls -l
fstat64(1, {st_mode=S_IFCHR|0600, st_rdev=makedev(136, 1), ...}) = 0
old_mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x40014000
write(1, "total 12\n", 9total 12
)               = 9
socket(PF_UNIX, SOCK_STREAM, 0)         = 3
connect(3, {sin_family=AF_UNIX, path="/var/run/.nscd_socket"}, 110) = 0
write(3, "\2\0\0\0\1\0\0\0\2\0\0\0", 12) = 12
write(3, "0\0", 2)                      = 2

and nothing until Ctrl+C.

With options -b -l -n lsof works and 
lsof -b -l -n | grep .nscd_socket | wc -l

gives 121 opened files and 

test: ~$cat /proc/sys/fs/file-nr                       
4931	2562	52425

so the number of opened files should not be the problem.
( for  i in `pgrep nscd` ; do ls /proc/$i/fd/ | wc -l ; done
or for  i in `pgrep slapd` ; do ls /proc/$i/fd/ | wc -l ; done
show not too many files and this is not related to

The only way to restore the machine is to kill nscd or slapd.

Our only way to have a stable (up to now) server is NOT to use

I think this bug could also be considered a security problem
since it may lead to a local DoS.

	Ciao and thanks.


-- System Information
Debian Release: 3.0
Architecture: i386
Kernel: Linux test 2.4.26 #3 SMP Tue Apr 27 15:53:14 CEST 2004 i686 unknown

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Date: Fri, 05 Aug 2005 19:15:42 +0900
Message-ID: <[🔎] 81psssu1td.wl%gotom@debian.or.jp>
From: GOTO Masanori <gotom@debian.org>
To: 153263-done@bugs.debian.org, 121396-done@bugs.debian.org,
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Subject: Close bugs tagged as woody
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These bugs are tagged as woody, because they're well-known problems
and for keeping open to come to light what the problem is.  However,
as you know, sarge was released.  Our stable version was moved from
woody to sarge.  It's high time to close old woody's bugs that are
still open.  Now I close these bugs.  If you have any objections to
close them, please reopen and let us know your trouble.

-- gotom

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