kernel-packages team mailing list archive

[Colin Ian King <1387214@xxxxxxxxxxxxxxxxxx>]

Made some progress today.

On the phone, I am seeing:

/var/lib/apparmor/profiles/click_com.ubuntu.filemanager_filemanager_0.3.275
containing a pathname and all zeros. The start is always on a page
boundary and the end is always on a page boundary.

I copied the entire partition /dev/mmcblk0p23 over adb back to my
laptop, mounted it and then mounted /mnt/ubuntu.img and the same file is
sane and not corrupted.  So the underlying data is OK.

corrupted data contains
/usr/share/click/preinstalled/com.ubuntu.music/1.3.625/apparmor.json

Cannot find any symlinks that would relate to this.

Next step, I'm adding debug into the symlink name to see if this appears
in the corrupt data to verify it is a symlink.

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https://bugs.launchpad.net/bugs/1387214

Title:
  file corruption on touch images in rw portions of the filesystem

Status in “linux” package in Ubuntu:
  Confirmed

Bug description:
  Symptoms are that cache files in /var/cache/apparmor and profiles in
  /var/lib/apparmor/profiles are sometimes corrupted after a reboot.
  We've already fixed several bugs in the apparmor and click-apparmor
  and made both more robust in the face of corruption and we've reduced
  the impact when there is a corrupted profile, but we've still not
  found the cause of the corruption. This corruption can still affect
  real-world devices: if a profile in /var/lib/apparmor/profiles is
  corrupted and the cache file is out of date, then the profile won't
  compile and that app/scope won't start.

  Workaround: remove the affected profile and then run 'sudo aa-
  clickhook'. This obviously is not viable on an end-user device.

  The investigation is ongoing and this may not be a problem with the
  kernel at all, so this bug may be retargeted to another project.

  The security team and the kernel team have discussed this a lot and
  Colin is currently looking at this. This bug is just so it can be
  tracked. Here is an excerpt from my latest email to Colin:

  "I believe I have conclusively ruled out apparmor_parser and aa-
  clickhook by creating a new 'home/bug/test-with-true.sh'. Here is the
  test output:

  http://paste.ubuntu.com/8648109/

  Specifically, home/bug/test-with-true.sh changes the interesting parts
  of the algorithm to:

  1. wait for unity8 to start (this ensures the apparmor upstart job is finished)
  2. restore apparmor_parser and aa-clickhook, if needed
  3. if /home/bug/profiles... exists, perform a diff -Naur /home/bug/profiles...
     /var/lib/apparmor/profiles and fail if differences (note, apparmor_parser
     and aa-clickhook were /bin/true during boot so they could not have changed
     /var/lib/apparmor/profiles)
  4. verify the profiles, exit with error if they do not
  5. alternately upgrade/downgrade the packages
  6. verify the profiles, exit with error if they do not
  7. copy the known good profiles in the previous step to /home/bug/profiles...
  8. have apparmor_parser and aa-clickhook point to /bin/true
  9. reboot
  10. go to step 1

  In the paste you'll notice that in step 6 the profiles were
  successfully created by the installation of the packages, then
  verified, then copied aside, then apparmor_parser and aa-clickhook
  diverted, then rebooted, only to have the profiles in
  /var/lib/apparmor/profiles be different than what was copied aside. It
  would be nice to verify on your device as well (I reproduced several
  times here) and verify the reproducer algorithm. I think this suggests
  this is a kernel issue and not userspace.

  IMPORTANT: you will want to update the reproducer and refollow all of these steps (ie, I updated the scripts, the debs, the sudoers file, etc):
  $ wget http://people.canonical.com/~jamie/cking/aa-corruption.tar.gz
  $ tar -zxvf ./aa-corruption.tar.gz
  ...

  $ adb push ./aa-corruption.tar.gz /tmp
  $ adb shell
  phablet@ubuntu-phablet:~$ cd /tmp
  phablet@ubuntu-phablet:~$ tar -zxvf ./aa-corruption.tar.gz
  phablet@ubuntu-phablet:~$ sudo mount -o remount,rw /
  phablet@ubuntu-phablet:~$ sudo cp ./aa-corruption/etc/sudoers.d/phablet
  /etc/sudoers.d/
  phablet@ubuntu-phablet:~$ sudo mount -o remount,ro /
  phablet@ubuntu-phablet:~$ sudo cp -a ./aa-corruption/home/bug /home
  phablet@ubuntu-phablet:~$ exit
  $ cd ./aa-corruption
  $ ./test-from-host.sh
  ...

  The old script is still in place. Simply adjust ./test-from-host.sh to have:
  testscript=/home/bug/test.sh
  #testscript=/home/bug/test-with-true.sh"

  The kernel team has verified the above reproducer and symptoms.

  Related bugs:
  * bug 1371771
  * bug 1371765
  * bug 1377338

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