Linking against libldap_r instead of libldap?

Linking against libldap_r instead of libldap?

[Leonardo Chiquitto]

Hi,

I'm investigating one segmentation fault report (multiple occurrences)
in automount where the OpenSSL context (using LDAP with TLS) is
clearly corrupted. Reading OpenSSL documentation I found that the
the library needs to be correctly initialized in order to run in a multi-
threaded environment. I also found that *only* the reentrant build of
the OpenLDAP libraries (libldap_r) initialize openssl for multi-threading.

By default (since commit 04dfd15590a) automount is linked against
libldap (non-reentrant), but I failed to find the reason behind the change.
Could you help me understand why it shouldn't be linked against
libldap_r?

Thanks,
Leonardo

Re: Linking against libldap_r instead of libldap?

[Ian Kent]

On Thu, 2013-06-27 at 22:42 -0300, Leonardo Chiquitto wrote:
> Hi,
> 
> I'm investigating one segmentation fault report (multiple occurrences)
> in automount where the OpenSSL context (using LDAP with TLS) is
> clearly corrupted. Reading OpenSSL documentation I found that the
> the library needs to be correctly initialized in order to run in a multi-
> threaded environment. I also found that *only* the reentrant build of
> the OpenLDAP libraries (libldap_r) initialize openssl for multi-threading.
> 
> By default (since commit 04dfd15590a) automount is linked against
> libldap (non-reentrant), but I failed to find the reason behind the change.
> Could you help me understand why it shouldn't be linked against
> libldap_r?

That was a long time ago, Jan 2008.
Sorry, I don't remember why I committed that change.

TBH I always thought the re-entrant version of the library should be
used so there must have been a case to justify not using it, I just
can't remember what it was.

Not a good change log entry either .....

Ian

Re: Linking against libldap_r instead of libldap?

[Ian Kent]

On Fri, 2013-06-28 at 14:31 +0800, Ian Kent wrote:
> On Thu, 2013-06-27 at 22:42 -0300, Leonardo Chiquitto wrote:
> > Hi,
> > 
> > I'm investigating one segmentation fault report (multiple occurrences)
> > in automount where the OpenSSL context (using LDAP with TLS) is
> > clearly corrupted. Reading OpenSSL documentation I found that the
> > the library needs to be correctly initialized in order to run in a multi-
> > threaded environment. I also found that *only* the reentrant build of
> > the OpenLDAP libraries (libldap_r) initialize openssl for multi-threading.
> > 
> > By default (since commit 04dfd15590a) automount is linked against
> > libldap (non-reentrant), but I failed to find the reason behind the change.
> > Could you help me understand why it shouldn't be linked against
> > libldap_r?
> 
> That was a long time ago, Jan 2008.
> Sorry, I don't remember why I committed that change.
> 
> TBH I always thought the re-entrant version of the library should be
> used so there must have been a case to justify not using it, I just
> can't remember what it was.
> 
> Not a good change log entry either .....

I've found a reference to the post this originated from:
http://www.mail-archive.com/autofs@linux.kernel.org/msg06499.html

I'm guessing the claim actually is that -D_REENTRANT should deal with
this although LDFLAGS contains -lpthread so perhaps this was actually a
problem with Mandriva.

In short:

Hello list.
Latest release (5.0.3) attempt to link against libldap_r, and fails on
mandriva because of unresolved pthread symbols. However, according to
ldap maintainer, libldap_r is supposed to be a private library. Hence
autofs should use -lldap, not -lldap_r. Attached patch fix this.
-- 
Guillaume Rousse
Moyens Informatiques - INRIA Futurs

Re: Linking against libldap_r instead of libldap?

[Leonardo Chiquitto]

On Fri, Jun 28, 2013 at 4:26 AM, Ian Kent <raven@themaw.net> wrote:
> On Fri, 2013-06-28 at 14:31 +0800, Ian Kent wrote:
>> On Thu, 2013-06-27 at 22:42 -0300, Leonardo Chiquitto wrote:
>> > Hi,
>> >
>> > I'm investigating one segmentation fault report (multiple occurrences)
>> > in automount where the OpenSSL context (using LDAP with TLS) is
>> > clearly corrupted. Reading OpenSSL documentation I found that the
>> > the library needs to be correctly initialized in order to run in a multi-
>> > threaded environment. I also found that *only* the reentrant build of
>> > the OpenLDAP libraries (libldap_r) initialize openssl for multi-threading.
>> >
>> > By default (since commit 04dfd15590a) automount is linked against
>> > libldap (non-reentrant), but I failed to find the reason behind the change.
>> > Could you help me understand why it shouldn't be linked against
>> > libldap_r?
>>
>> That was a long time ago, Jan 2008.
>> Sorry, I don't remember why I committed that change.
>>
>> TBH I always thought the re-entrant version of the library should be
>> used so there must have been a case to justify not using it, I just
>> can't remember what it was.
>>
>> Not a good change log entry either .....
>
> I've found a reference to the post this originated from:
> http://www.mail-archive.com/autofs@linux.kernel.org/msg06499.html
>
> I'm guessing the claim actually is that -D_REENTRANT should deal with
> this although LDFLAGS contains -lpthread so perhaps this was actually a
> problem with Mandriva.
>
> In short:
>
> Hello list.
> Latest release (5.0.3) attempt to link against libldap_r, and fails on
> mandriva because of unresolved pthread symbols. However, according to
> ldap maintainer, libldap_r is supposed to be a private library. Hence
> autofs should use -lldap, not -lldap_r. Attached patch fix this.

Thanks for digging that info in the archives, Ian. I finally had more time
to investigate the problem reported to us and it seems to be a valid one.

I'm going to write a separate email with the complete report and proposed
solution.

Thanks,
Leonardo