[Bug 270781] Re: unix_chkpwd abnormal exit: 11 unix_chkpwd crashes under gnome-screensaver and prevents unlock (/dev/null corruption?)

[Steve Langasek]

https://bugzilla.redhat.com/show_bug.cgi?id=488147#c21 explains that
this segfault comes not from unix_chkpwd, but from glibc which aborts
when a setuid or setgid application is started without fds (0,1,2) open
and opening a placeholder fd to either /dev/null or /dev/full fails with
a permissions problem.

And fds 1 and 2 are closed by pam_unix before launching unix_chkpwd,
which is what triggers the abort.

Ultimately the bug is in whatever has broken the standard devices on the
system, preventing the fds from being reopened.  But we may be able to
defend against this better by just not closing stdout/stderr in the
first place.

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https://bugs.launchpad.net/bugs/270781

Title:
  unix_chkpwd abnormal exit: 11 unix_chkpwd crashes under  gnome-
  screensaver and prevents unlock (/dev/null corruption?)

Status in “pam” package in Ubuntu:
  Triaged
Status in “pam” package in Fedora:
  Unknown

Bug description:
  Binary package hint: libpam-modules

  I am running Ubuntu Hardy 32-Bit on a Thinkpad T61 with all updates
  available today. The gnome screensaver locks my screen after 10
  minutes idle automatically. Now in the password dialogue I can enter
  any password or string and the screen gets unlocked. In syslog you'll
  find the following error message simultaneously:

   kernel: [32810.156696] unix_chkpwd[4787] general protection
  eip:b7f86446 esp:bfd2d31c error:0

  But when I lock my screen manually, this bug doesn't occur and I have
  to type the right password to unlock the screen again.

  Some more informations:

  # lsb_release -rd
  Description:	Ubuntu 8.04.1
  Release:	8.04

  # apt-cache policy libpam-modules
  libpam-modules:
    Installed: 0.99.7.1-5ubuntu6.1
    Candidate: 0.99.7.1-5ubuntu6.1
    Version table:
   *** 0.99.7.1-5ubuntu6.1 0
          500 http://de.archive.ubuntu.com hardy-updates/main Packages
          100 /var/lib/dpkg/status
       0.99.7.1-5ubuntu6 0
          500 http://de.archive.ubuntu.com hardy/main Packages

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