Debian Bug report logs - #684645
liblockfile1: Order of fcntl and dotlock in maillock

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Message #5 received at submit@bugs.debian.org (full text, mbox, reply):

From: Paul Szabo <paul.szabo@sydney.edu.au>

To: Debian Bug Tracking System <submit@bugs.debian.org>

Subject: liblockfile1: Order of fcntl and dotlock in maillock

Date: Sun, 12 Aug 2012 22:34:57 +1000

Package: liblockfile1
Version: 1.09-4
Severity: serious
Justification: Policy 11.6

Debian policy
http://www.debian.org/doc/debian-policy/ch-customized-programs.html#s-mail-transport-agents
says:
  ... fcntl() locking must be combined with dot locking.
  To avoid deadlocks, a program should use fcntl() first
  and dot locking after this, or alternatively implement
  the two locking methods in a non blocking way. Using
  the functions maillock and mailunlock provided by the
  liblockfile* packages is the recommended way to
  realize this. 
Looking at an strace of /usr/lib/sm.bin/mail.local it seems to use
/usr/lib/i386-linux-gnu/liblockfile.so.1 and shows:
  link("/var/mail/.lk10336dp639", "/var/mail/psz.lock") = 0
  open("/var/mail/psz", O_WRONLY|O_APPEND) = 4
  fcntl64(4, F_SETLKW, {type=F_WRLCK, whence=SEEK_CUR, start=0, len=0}) = 0
which seems the wrong order.

Please see http://bugs.debian.org/648941 also.

Thanks, Paul

Paul Szabo   psz@maths.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics   University of Sydney    Australia


-- System Information:
Debian Release: wheezy/sid
  APT prefers testing
  APT policy: (500, 'testing')
Architecture: i386 (i686)

Kernel: Linux 3.2.21-pk06.02-i386 (SMP w/2 CPU cores)
Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968)
Shell: /bin/sh linked to /bin/bash

Versions of packages liblockfile1 depends on:
ii  libc6              2.13-33
ii  liblockfile-bin    1.09-4
ii  multiarch-support  2.13-33

liblockfile1 recommends no packages.

liblockfile1 suggests no packages.

-- no debconf information

Message #16 received at 684645@bugs.debian.org (full text, mbox, reply):

From: paul.szabo@sydney.edu.au

To: 684645@bugs.debian.org

Cc: control@bugs.debian.org

Subject: /usr/lib/sm.bin/mail.local: Order of fcntl and dotlock in maillock

Date: Mon, 13 Aug 2012 08:12:51 +1000

reassign 684645 sendmail-bin 8.14.4-2.1
thanks

Hmm... comparing with an strace of /usr/bin/bsd-mailx, shows that mailx
uses liblockfile and does:
  open("/var/mail/psz", O_RDWR)     = 3
  fcntl64(3, F_SETLKW, {type=F_WRLCK, whence=SEEK_CUR, start=0, len=0}) = 0
  link("/var/mail/.lk128035p639", "/var/mail/psz.lock") = 0
in the "right" order. This suggests that liblockfile is fine.

I thus suppose that mail.local only "pretends" to use liblockfile and
maillock(), but that in fact it does its own locking, this bug being
entirely in the sendmail-bin sources. - Such "pretence" was noted
previously, in the initial report of  http://bugs.debian.org/648941 .

Cheers, Paul

Paul Szabo   psz@maths.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics   University of Sydney    Australia

Message #21 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Andreas Beckmann <debian@abeckmann.de>

To: paul.szabo@sydney.edu.au

Cc: 684645@bugs.debian.org

Subject: Re: Bug#684645: /usr/lib/sm.bin/mail.local: Order of fcntl and dotlock in maillock

Date: Tue, 2 Oct 2012 03:46:42 +0200

In case someone wants to tackle this RC bug, the GIT repository I created for 
working on a fix for bug #681147 may be helpful:

git://github.com/anbe42/sendmail.git

branches: upstream, master, bug-681147

See also #689379


Andreas

Message #26 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Michael Stapelberg <stapelberg@debian.org>

To: Paul Szabo <paul.szabo@sydney.edu.au>

Cc: 684645@bugs.debian.org

Subject: Re: liblockfile1: Order of fcntl and dotlock in maillock

Date: Sat, 27 Oct 2012 00:29:37 +0200

Hi Paul,

On Sun, 12 Aug 2012 22:34:57 +1000
Paul Szabo <paul.szabo@sydney.edu.au> wrote:
>   ... fcntl() locking must be combined with dot locking.
>   To avoid deadlocks, a program should use fcntl() first
>   and dot locking after this, or alternatively implement
>   the two locking methods in a non blocking way[100]. Using
>   the functions maillock and mailunlock provided by the
>   liblockfile* packages is the recommended way to
>   realize this.
> Looking at an strace of /usr/lib/sm.bin/mail.local it seems to use
> /usr/lib/i386-linux-gnu/liblockfile.so.1 and shows:
>   link("/var/mail/.lk10336dp639", "/var/mail/psz.lock") = 0
>   open("/var/mail/psz", O_WRONLY|O_APPEND) = 4
>   fcntl64(4, F_SETLKW, {type=F_WRLCK, whence=SEEK_CUR, start=0,
> len=0}) = 0 which seems the wrong order.
In mail.local.c:deliver(), line 1109, lockmbox() is called and in line
1268, flock() is called blockingly (without LOCK_NB).

So: yes, I think you are right and I think this is a violation of the
policy. Unfortunately, I have far too little knowledge about sendmail
and NFS-safe locking, so I cannot submit a patch.

It might be helpful to include some basic instructions for non-sendmail
users on how to reproduce the issue at hand, just in case someone comes
along who knows about file locking and is willing to dive into
sendmail :-).

-- 
Best regards,
Michael

Message #31 received at 684645@bugs.debian.org (full text, mbox, reply):

From: paul.szabo@sydney.edu.au

To: stapelberg@debian.org

Cc: 684645@bugs.debian.org

Subject: Re: liblockfile1: Order of fcntl and dotlock in maillock

Date: Sat, 27 Oct 2012 21:03:14 +1100

Dear Michael,

I guess that lockmbox() should not be called on entry to deliver(),
but that block moved to after the first flock().

I wonder about the close(mbfd) in line 1370: should unlockmbox() be
called just after, and lockmbox() called again after the re-open and
subsequent flock()?

---

I wonder if I am qualified to provide patches. What has me stumped
is that I do not seem to be able to build sendmail-bin. Trying:

  tar zxf sendmail.8.14.4.tar.gz
  gzcat sendmail_8.14.4-2.1.diff.gz | patch -p0
  cd sendmail-8.14.4
  dpkg-buildpackage -rfakeroot -B -uc -us

elicits some errors:

... 
 fakeroot debian/rules clean
/usr/share/cdbs/1/rules/tarball.mk:33: WARNING:  tarball.mk is deprecated - please use source format 3.0 instead
/bin/sh: line 0: cd: build-tree/sendmail-8.14.4: No such file or directory
...
dh_testroot
rm -f debian/stamp-makefile-build debian/stamp-makefile-install
k distclean
make: k: Command not found
...
cd build-tree/sendmail-8.14.4 && QUILT_PATCHES=/usr/users/amstaff/psz/sendmail-bin/sendmail-8.14.4/debian/patches/8.14/8.14.4 quilt --quiltrc /dev/null push -a || test $? = 2
Applying patch control_c
can't find file to patch at input line 24
...
make: *** [debian/stamp-patched] Error 1
dpkg-buildpackage: error: debian/rules build-arch gave error exit status 2

Can you give me a hint on what I am doing wrong?

Thanks, Paul

Paul Szabo   psz@maths.usyd.edu.au   http://www.maths.usyd.edu.au/u/psz/
School of Mathematics and Statistics   University of Sydney    Australia

Message #36 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Michael Stapelberg <stapelberg@debian.org>

To: paul.szabo@sydney.edu.au

Cc: 684645@bugs.debian.org

Subject: Re: liblockfile1: Order of fcntl and dotlock in maillock

Date: Wed, 31 Oct 2012 09:33:54 +0100

Hi paul,

paul.szabo@sydney.edu.au writes:
> I wonder if I am qualified to provide patches. What has me stumped
> is that I do not seem to be able to build sendmail-bin. Trying:
>
>   tar zxf sendmail.8.14.4.tar.gz
>   gzcat sendmail_8.14.4-2.1.diff.gz | patch -p0
>   cd sendmail-8.14.4
>   dpkg-buildpackage -rfakeroot -B -uc -us
>
> elicits some errors:
You can use the following commands to build sendmail:

apt-get build-dep sendmail
apt-get source sendmail
cd sendmail-8.14.4
dpkg-buildpackage -sa

-- 
Best regards,
Michael

Message #43 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Tim Marston <tim@ed.am>

To: 684645@bugs.debian.org

Subject: Re: Patch

Date: Sun, 27 Jan 2013 15:17:26 +0000

[Message part 1 (text/plain, inline)]

Sorry, it would probably be more useful if were to submit the correct
patch!

-- 
Tim Marston
ed.am

[patch (text/plain, attachment)]

Message #48 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Tim Marston <tim@ed.am>

To: 684645@bugs.debian.org

Subject: Patch

Date: Sun, 27 Jan 2013 15:01:22 +0000

[Message part 1 (text/plain, inline)]

Hi,

I've attached a patch to do the lockmbox() after open()ing and
lockf()ing the mailbox, and conversely to unlockmbox() before
close()ing it.  Looking at the strace, it now goes...

  open("/var/mail/edam", O_WRONLY|O_APPEND) = 4
  fcntl64(4, F_SETLKW, {type=F_WRLCK, whence=SEEK_CUR, start=0, len=0}) = 0
  link("/var/mail/.lk06598ddebian-dev", "/var/mail/edam.lock") = 0
  ...
  unlink("/var/mail/edam.lock")           = 0
  close(4)                                = 0

Someone with more experience of locking should verify there are no
problems with this.  :o)

-- 
Tim Marston
ed.am

[patch (text/plain, attachment)]

Message #53 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Michael Stapelberg <stapelberg@debian.org>

To: Jakub Safarik <jsafarik@ymail.com>

Cc: Tim Marston <tim@ed.am>, 684645@bugs.debian.org

Subject: Re: Patch

Date: Tue, 5 Feb 2013 21:12:02 +0100

Hi Jakub,

Since you intend to adopt the sendmail package, can you have a look at
the patch which Tim posted at
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=684645#43 please?

If you need a sponsor for your upload, I can help you with that.

-- 
Best regards,
Michael

Message #58 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Jakub Safarik <jsafarik@ymail.com>

To: Michael Stapelberg <stapelberg@debian.org>

Cc: Tim Marston <tim@ed.am>, 684645@bugs.debian.org

Subject: Re: Patch

Date: Sat, 09 Feb 2013 18:08:47 +0100

Hi Michael,

I looked at it and uploaded a new package version to the mentors site.
It does locking in correct order as Tim showed in his strace output
before.
I have read the patch carefully and from what I can see there is no
problem with it. But again, someone with more experience of locking
should verify that.

--
Best regards,
Jakub Safarik


On Tue, 2013-02-05 at 21:12 +0100, Michael Stapelberg wrote:
> Hi Jakub,
> 
> Since you intend to adopt the sendmail package, can you have a look at
> the patch which Tim posted at
> http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=684645#43 please?
> 
> If you need a sponsor for your upload, I can help you with that.
> 

Message #63 received at 684645-close@bugs.debian.org (full text, mbox, reply):

From: Jakub Safarik <jsafarik@ymail.com>

To: 684645-close@bugs.debian.org

Subject: Bug#684645: fixed in sendmail 8.14.4-4

Date: Mon, 11 Feb 2013 11:32:51 +0000

Source: sendmail
Source-Version: 8.14.4-4

We believe that the bug you reported is fixed in the latest version of
sendmail, which is due to be installed in the Debian FTP archive.

A summary of the changes between this version and the previous one is
attached.

Thank you for reporting the bug, which will now be closed.  If you
have further comments please address them to 684645@bugs.debian.org,
and the maintainer will reopen the bug report if appropriate.

Debian distribution maintenance software
pp.
Jakub Safarik <jsafarik@ymail.com> (supplier of updated sendmail package)

(This message was generated automatically at their request; if you
believe that there is a problem with it please contact the archive
administrators by mailing ftpmaster@debian.org)


-----BEGIN PGP SIGNED MESSAGE-----
Hash: SHA512

Format: 1.8
Date: Wed, 06 Feb 2013 17:33:44 +0100
Source: sendmail
Binary: sendmail-bin rmail sensible-mda libmilter1.0.1 libmilter1.0.1-dbg libmilter-dev sendmail-doc sendmail sendmail-base sendmail-cf
Architecture: source all amd64
Version: 8.14.4-4
Distribution: unstable
Urgency: low
Maintainer: Jakub Safarik <jsafarik@ymail.com>
Changed-By: Jakub Safarik <jsafarik@ymail.com>
Description: 
 libmilter-dev - Sendmail Mail Filter API (Milter)
 libmilter1.0.1 - Sendmail Mail Filter API (Milter)
 libmilter1.0.1-dbg - Sendmail Mail Filter API (Milter)
 rmail      - MTA->UUCP remote mail handler
 sendmail   - powerful, efficient, and scalable Mail Transport Agent
 sendmail-base - powerful, efficient, and scalable Mail Transport Agent
 sendmail-bin - powerful, efficient, and scalable Mail Transport Agent
 sendmail-cf - powerful, efficient, and scalable Mail Transport Agent
 sendmail-doc - powerful, efficient, and scalable Mail Transport Agent
 sensible-mda - Mail Delivery Agent wrapper
Closes: 684645 699117
Changes: 
 sendmail (8.14.4-4) unstable; urgency=low
 .
   * New maintainer. (Closes: #699117)
   * New patch: lock-mail-local (thanks to Tim Marston)
     - fix order of fcntl and dotlock in mail.local. (Closes: #684645)
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Message #68 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Demetris Demetriou <mitsosgtir@gmail.com>

To: 684645@bugs.debian.org

Subject: Package stuck in migration

Date: Wed, 10 Apr 2013 17:03:17 +0300

[Message part 1 (text/plain, inline)]

Hello,
Package tracking page shows:


   testing migration

excuses <http://qa.debian.org/excuses.php?package=sendmail>:

 * 57 days old (needed 10 days)
 * Not touching package due to block request by freeze (contact
   debian-release if update is needed)
 * Updating sendmail-bin fixes old bugs: #684645
   <http://bugs.debian.org/684645>
 * Not considered

Since this is a fix for an RC bug, can you, as the maintainer please 
submit an unblock request?
Thank you.

[Message part 2 (text/html, inline)]

Message #73 received at 684645@bugs.debian.org (full text, mbox, reply):

From: Andreas Beckmann <anbe@debian.org>

To: Demetris Demetriou <mitsosgtir@gmail.com>, 684645@bugs.debian.org

Subject: Re: Bug#684645: Package stuck in migration

Date: Wed, 10 Apr 2013 18:42:49 +0200

On 2013-04-10 16:03, Demetris Demetriou wrote:
> Since this is a fix for an RC bug, can you, as the maintainer please
> submit an unblock request?

#699344


Andreas

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