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Re: Problem with rwm overlay when used with translucent

Bryan Mesich wrote: 
Good afternoon to all,

I've been trying to track down a problem that has been eluding me
for the past week and I think I've narrowed it down to the rwm
overlay. When the rwm overlay is used in conjunction with the
translucent overlay, slapd dies with the following error and backtrace:

*** glibc detected *** ./libexec/slapd: double free or corruption
(fasttop): 0x0860ca38 ***

======= Backtrace: =========
/lib/libc.so.6[0x5ceac1]
/lib/libc.so.6(cfree+0x90)[0x5d20f0]
./libexec/slapd(do_search+0x10e)[0x807bbfe]
./libexec/slapd[0x8079845]
./libexec/slapd[0x8079c12]
./libexec/slapd[0x816d504]
/lib/libpthread.so.0[0x6f750b]
/lib/libc.so.6(clone+0x5e)[0x638b2e]

(I have the memory map if its useful)

I have been able to reproduce this error in 2.4.11, 2.4.13 and
the CVS HEAD as of Mon Feb  9 11:13:04 CST 2009.

I haven't found any documentation that mentions limitations
and/or bugs when using rwm with translucent. Here is portion of
my configuration file (am I stacking the overlays correctly?): 

###############################################

# database backend modules to load
moduleload      back_ldap.la

# overlay modules to load
moduleload     translucent.la
moduleload     rwm.la

# local database
database        bdb
suffix          "dc=nodak,dc=edu"
rootdn          "cn=root,dc=nodak,dc=edu"
rootpw          secret
directory       /var/lib/ldap2.4

overlay translucent
uri "ldap://ldap.nodak.edu/";;


                          ^^^^^^ there is an error here

overlay rwm
#rwm-rewriteEngine on
#rwm-rewriteContext searchFilter
#rwm-rewriteRule "^(.*objectClass=)posixAccount(.*)" "$1inetOrgPerson$2" ":@"
#rwm-map attribute uidNumber NID

###############################################

The use case for this configuration is to create a custom view
for clients who are using nss ldap. I'm using a translucent
overlay to provide attributes that are missing on the remote
server. The rwm overlay is used to map attributes that exist, but are named differently on the remote server. I'm also using a rewrite rule to manipulate incoming search filters.

Simply declaring the rwm overlay (as shown in my configuration)
is enough to produce the error when used with a translucent
overlay. slapd will usually answer one request after being started before tipping over.

I can file an ITS if need be, but I thought I'd ask before doing
so.  Maybe my configuration is wrong or I have missed a piece of
documentation explaining why my configuration doesn't work.

I suggest you file an ITS. The reason for this double free is that the cleanup call of slapo-rwm deletes the filterstr set by slapo-rwm and replaces it with the original one. However, the translucent_search() call subsequently sets the now deleted pointer to slapo-rwm's filterstr into the operation structure.

This needs to be reworked, and the ITS will allow to track this rework.

p.


Ing. Pierangelo Masarati
OpenLDAP Core Team

SysNet s.r.l.
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