Debian Bug report logs - #626482
libc0.1: 2.13 causes segfaults + bus errors inside DSA's dchroots

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

From: Axel Beckert <abe@debian.org>

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

Subject: libc0.1: 2.13 causes segfaults + bus errors inside DSA's dchroots on kfreebsd-*

Date: Thu, 12 May 2011 12:15:48 +0200 (CEST)

Package: libc0.1
Version: 2.13-2
Severity: important
User: debian-bsd@lists.debian.org
Usertags: kfreebsd

[Mostly a summary of
 http://lists.debian.org/debian-bsd/2011/05/msg00038.html and
 http://lists.debian.org/debian-bsd/2011/05/msg00039.html]

After dist-upgrading libc0.1 and friends (i.e. all(*) installed packages
which are also built from eglibc source) from 2.11.2-something to 2.13-2
inside io's and asdfasdf's sid, calling "dchroot sid" segfaults on io
and causes bus errors on asdfasdf:

io:~# dchroot sid /bin/true
Segmentation fault
io:~# dchroot sid
Segmentation fault
io:~# 

asdfasdf:~# dchroot sid /bin/true
Bus error
asdfasdf:~# dchroot sid
Bus error
asdfasdf:~# 

Ah normal (but root only) "chroot /srv/chroot/sid" works on both
machines, so I could at least fix it from the inside by downgrading
libc0.1 and friends back to 2.11.2-13.

Please note that the used dchroot command comes from DSA's version of
dchroot-dsa (version 2:1.1), not from the one in the Debian archive. The
latter does not show this problem according to Petr Salinger.

I'm not sure where exactly the causing bug is located, it could be in
eglibc, in DSA's dchroot, and maybe also in gcc-4.6 (with which libc0.1
2.13-2 very likely has been compiled). But as downgrading libc0.1 and
friends helped to fix this regression, I'm filing it against libc0.1.

I'm not filing this as RC as it is not yet reproducible with only
packages from the official archive, but since porterboxes are affected
I doubt that this is a less important issue.

So feel free to raise the severity and/or reassign this bug.

(*) locales is definitely not relevant here as I initially by accident
    just downgraded all architecture-dependent packages built from the
    eglibc source.

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

Kernel: kFreeBSD 8.2-1-686
Locale: LANG=en_US.iso885915, LC_CTYPE=en_US.iso885915 (charmap=ISO-8859-15)
Shell: /bin/sh linked to /bin/dash

Versions of packages libc0.1 depends on:
ii  libc-bin                      2.13-2  Embedded GNU C Library: Binaries
ii  libgcc1                       1:4.6.0-7  GCC support library

Versions of packages libc0.1 recommends:
pn  libc0.1-i686                  <none>     (no description available)

Versions of packages libc0.1 suggests:
ii  debconf [debconf-2.0]         1.5.39     Debian configuration management sy
pn  glibc-doc                     <none>     (no description available)
ii  locales                       2.13-2  Embedded GNU C Library: National L
ii  locales-all [locales]         2.13-2  Embedded GNU C Library: Precompile

-- debconf information:
* glibc/restart-services: cron
  glibc/disable-screensaver:
  glibc/restart-failed:
  glibc/upgrade: true

Message #10 received at 626482@bugs.debian.org (full text, mbox, reply):

From: Axel Beckert <abe@debian.org>

To: debian-bsd@lists.debian.org

Cc: admin@io.debian.net, 626482@bugs.debian.org

Subject: Re: sid chroots on io and asdfasdf currently broken

Date: Thu, 12 May 2011 12:36:52 +0200

Hi,

taking the discussion back to debian-bsd@l.d.o and to the bug report I
filed just before Aurelien's mail came in.

Aurelien Jarno wrote:
> > Will probably file a bug report soon. I'm still not sure against
> > which package, but I'll probably choose libc0.1.
> 
> The problem seems to be a conflict between libnss-db outside the chroot
> and inside the chroot. dchroot-dsa calls initgroup("root", 0) after
> chrooting, but before doing an execve, and that causes the crash.
> 
> Disabling libnss-db either inside or outside the chroot workarounds the
> problem.

Ok, will try that on io soon as libnss-db is removed from the sid
chroot there already.

		Regards, Axel
-- 
 ,''`.  |  Axel Beckert <abe@debian.org>, http://people.debian.org/~abe/
: :' :  |  Debian Developer, ftp.ch.debian.org Admin
`. `'   |  1024D: F067 EA27 26B9 C3FC 1486  202E C09E 1D89 9593 0EDE
  `-    |  4096R: 2517 B724 C5F6 CA99 5329  6E61 2FF9 CD59 6126 16B5

Message #15 received at 626482@bugs.debian.org (full text, mbox, reply):

From: Aurelien Jarno <aurelien@aurel32.net>

To: Axel Beckert <abe@debian.org>, 626482@bugs.debian.org

Subject: Re: Bug#626482: libc0.1: 2.13 causes segfaults + bus errors inside DSA's dchroots on kfreebsd-*

Date: Thu, 12 May 2011 14:41:33 +0200

On Thu, May 12, 2011 at 12:15:48PM +0200, Axel Beckert wrote:
> Package: libc0.1
> Version: 2.13-2
> Severity: important
> User: debian-bsd@lists.debian.org
> Usertags: kfreebsd
> 
> [Mostly a summary of
>  http://lists.debian.org/debian-bsd/2011/05/msg00038.html and
>  http://lists.debian.org/debian-bsd/2011/05/msg00039.html]
> 
> After dist-upgrading libc0.1 and friends (i.e. all(*) installed packages
> which are also built from eglibc source) from 2.11.2-something to 2.13-2
> inside io's and asdfasdf's sid, calling "dchroot sid" segfaults on io
> and causes bus errors on asdfasdf:
> 
> io:~# dchroot sid /bin/true
> Segmentation fault
> io:~# dchroot sid
> Segmentation fault
> io:~# 
> 
> asdfasdf:~# dchroot sid /bin/true
> Bus error
> asdfasdf:~# dchroot sid
> Bus error
> asdfasdf:~# 
> 
> Ah normal (but root only) "chroot /srv/chroot/sid" works on both
> machines, so I could at least fix it from the inside by downgrading
> libc0.1 and friends back to 2.11.2-13.
> 
> Please note that the used dchroot command comes from DSA's version of
> dchroot-dsa (version 2:1.1), not from the one in the Debian archive. The
> latter does not show this problem according to Petr Salinger.
> 
> I'm not sure where exactly the causing bug is located, it could be in
> eglibc, in DSA's dchroot, and maybe also in gcc-4.6 (with which libc0.1
> 2.13-2 very likely has been compiled). But as downgrading libc0.1 and
> friends helped to fix this regression, I'm filing it against libc0.1.
> 
> I'm not filing this as RC as it is not yet reproducible with only
> packages from the official archive, but since porterboxes are affected
> I doubt that this is a less important issue.


First of all please note that this problem is not GNU/kFreeBSD specific, but
can easily reproduced on GNU/Linux. 

The problems comes from the fact that dchroot calls chroot() to actually
chroot into a directory, and after calls libc functions which can 
trigger library loading. It means that the version of the library in the
chroot will end-up in the same memory space that libraries inside the 
chroot, and they might not be compatible. In our case, the call to 
initgroups() after chroot() might load libnss-db from the chroot 
(depending on some conditions, mainly if the user is defined in 
/etc/passwd or in the nss database inside and outside the chroot), and 
libnss-db as most libnss libraries has a strong dependency on the libc 
version.

> So feel free to raise the severity and/or reassign this bug.
> 

IMHO the bug is in dchroot-dsa, but given the version we are using is
not in the archive, I can't reassign it.

-- 
Aurelien Jarno	                        GPG: 1024D/F1BCDB73
aurelien@aurel32.net                 http://www.aurel32.net

Message #40 received at 626482-done@bugs.debian.org (full text, mbox, reply):

From: Steven Chamberlain <steven@pyro.eu.org>

To: 626482-done@bugs.debian.org

Subject: Re: Bug#626482: libc0.1: 2.13 causes segfaults + bus errors inside DSA's dchroots

Date: Wed, 22 Oct 2014 00:17:50 +0100

Source-Version: 2.19-11

Not reproducible with sid/jessie glibc.

Regards,
-- 
Steven Chamberlain
steven@pyro.eu.org

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