[Cosmic][SRU Bionic/Xenial/Trusty][PATCH 0/2] Fixes for partition scan of corrupted AIX disk

[Mauricio Faria de Oliveira]

BugLink: https://bugs.launchpad.net/bugs/1787281

[Impact]

 * Users with disks/LUNs used for AIX operating system installations
   previously, which possibly undergone overwrites/corruption on the
   partition table, might hit kernel failures during partition scan
   of such disk/LUN, and possibly hang the system (seen with retries).

 * The Linux kernel should be robust to corrupted disk data, performing
   a better sanitization/checks and not failing.

 * The fix are a couple of simple logic changes to make the code
   of the AIX partition table parser more robust.

[Test Case]

 * Run the partition scan on the (trimmed) disk image of the AIX lun.
   (It's not provided here since it contains customer data), with this
   command:

   $ sudo losetup --find --show --partscan rlv_grkgld.1mb

 * On failure, the command hangs, and messages like these are printed
   to the console, depending on the kernel version (see tests below)

   [ 270.506420] partition (null) (3 pp's found) is not contiguous

   [ 270.597428] BUG: unable to handle kernel paging request at 0000000000001000
   [ 270.599525] IP: [<ffffffff81379d4d>] strnlen+0xd/0x40

 * On success, the command prints a loop device name, for example:

   /dev/loop0

[Regression Potential]

 * Low. Both changes are simple improvements in logic.

 * This affects users which mount disks/LUNs from the AIX OS;
   it should only change behavior for users which relied on a
   uninitialized variables to work correctly during partition
   scan of those disks/LUNs which should be rare as the code
   is likely to fail as we observe in this scenario.

 * This has been tested on Cosmic, Bionic, Xenial, and Trusty.

Mauricio Faria de Oliveira (2):
  partitions/aix: fix usage of uninitialized lv_info and lvname
    structures
  partitions/aix: append null character to print data from disk

 block/partitions/aix.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

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2.17.1