[Bug 1905393] Re: Ubuntu 20.04: opal-prd fails to start on 20.04

[Brian Murray]

** Changed in: skiboot (Ubuntu Focal)
    Milestone: ubuntu-20.04.2 => focal-updates

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https://bugs.launchpad.net/bugs/1905393

Title:
  Ubuntu 20.04: opal-prd fails to start on 20.04

Status in The Ubuntu-power-systems project:
  In Progress
Status in skiboot package in Ubuntu:
  Fix Released
Status in skiboot source package in Focal:
  In Progress
Status in skiboot source package in Groovy:
  In Progress
Status in skiboot source package in Hirsute:
  Fix Released

Bug description:
  [Impact]

  This impacts the opal-prd userspace command from the skiboot package

  On systems using recent versions of systemd /dev (devtmpfs) is mounted
  with noexec option. Such mount prevents mapping HBRT image code region
  as RWX from /dev. This commit, as suggested in github PR linked below,
  attempts to work around the situation by copying HBRT image to anon
  mmaped memory region and sets mprotect rwx on it, allowing opal-prd to
  successfully execute the code region.

  The direct Impact is that the opal-prd command will not start on
  groovy and focal

  [Test Case]

  Unfortunately due to the specific hardware requirement I wasn't able
  to reproduce this problem and provide a test case for it. However I
  was able to build this package into a ppa and got the IBM team to
  confirm this problem was resolved for groovy focal, bionic, xenial see
  comment #4

  I would anticipate this test should work based on the description
  $> opal-prd
  contemplate crash
  $> sudo apt update skiboot
  $> opal-prd
  no crash with the updated package

  [What could go wrong]

  Hopefully not much. The initial fix was prepared back in October and I
  would think regression could have been discovered by now. The change
  is also limited to single user space command that IBM is closely using
  and maintaining. I anticipate regression to be reported to us
  promptly.

  [Original Description]

  == Comment: #0 - VASANT HEGDE <hegdevasant at in.ibm.com> - 2020-11-23 23:23:22 ==
  ---Problem Description---
  opal-prd fails to start on 20.04

  Contact Information = Vasant hegde <hegdevasant at linux.vnet.ibm.com>

  ---uname output---
  Ubuntu 20.04

  Machine Type = All Power System

  ---Steps to Reproduce---
   opal-prd fails to start on 20.04

  Userspace tool common name: opal-prd

  The userspace tool has the following bit modes: 64bit

  Userspace rpm: opal-prd

  This is fixed in upstream by below commit. Please backport this patch
  to 20.04 LTS release. Also applicable for 20.10.

  commit 47005e8d4c9aeda5826c17c4a013cfbda1a3f2de
  Author: Georgy Yakovlev <gyakovlev at gentoo.org>
  Date:   Mon Oct 12 14:29:17 2020 -0700

      opal-prd: handle devtmpfs mounted with noexec

      On systems using recent versions of systemd /dev (devtmpfs) is mounted with
      noexec option. Such mount prevents mapping HBRT image code region as RWX
      from /dev. This commit, as suggested in github PR linked below, attempts to
      work around the situation by copying HBRT image to anon mmaped memory
      region and sets mprotect rwx on it, allowing opal-prd to sucessfully
      execute the code region.

      Having memory region set as RWX is not ideal for security, but fixing that
      is a separate and hard to solve problem. Original code also mmaped region
      as RWX, so this PR does not make things worse at least.

      Closes: https://github.com/open-power/skiboot/issues/258
      Signed-off-by: Georgy Yakovlev <gyakovlev at gentoo.org>
      Reviewed-by: Vasant Hegde <hegdevasant at linux.vnet.ibm.com>
      [oliver: whitespace fix, add a comment, reflow commit message]
      Signed-off-by: Oliver O'Halloran <oohall at gmail.com>

  -Vasant

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