[Bug 1883016] [NEW] revert tmpfiles.d loading of microcode

[Dimitri John Ledkov]

*** This bug is a security vulnerability ***

Public security bug reported:

[Impact]

revert tmpfiles.d loading of microcode

Sometimes, despite intensive testing bad microcode can be shipped.

When bad microcode is shipped and it is attempted to be loaded at
package configuration time, system will end up in inconsistent state.
Specifically apt transaction is aborted, new microcode is unpacked on
disk but dpkg database is in inconsistent state.

Thus whilst it was meant to be a canary, it wasn't a good one. Also it
applies on initrd-less boot, initrd-full boot, early initrd and package
upgrades. Which is not the right design here.

Ideally, installing microcode update would generate a one time boot
option to try new microcode, if successful commit booting with it.
Otherwise fallback to previous version of the microcode. None of that is
solvable with tmpfiles however.

Most recent examples is the Skylake regression on 0x000406e3 systems

https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1882890
https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1883002

[Test Case]

 * downgrade to old intel-microcode package
 * reboot
 * upgrade to new intel-microcode package
 * observe that uncoordinate microcode update is not attempted at package configuration time

[Regression Potential]

 * This is a revert

[Other Info]
 
 * microcode try, commit or revert would be nice to implement.

** Affects: intel-microcode (Ubuntu)
     Importance: Undecided
         Status: In Progress

** Affects: intel-microcode (Ubuntu Eoan)
     Importance: Undecided
         Status: In Progress

** Affects: intel-microcode (Ubuntu Focal)
     Importance: Undecided
         Status: In Progress

** Affects: intel-microcode (Ubuntu Groovy)
     Importance: Undecided
         Status: In Progress

** Also affects: intel-microcode (Ubuntu Eoan)
   Importance: Undecided
       Status: New

** Also affects: intel-microcode (Ubuntu Groovy)
   Importance: Undecided
       Status: New

** Also affects: intel-microcode (Ubuntu Focal)
   Importance: Undecided
       Status: New

** Changed in: intel-microcode (Ubuntu Groovy)
       Status: New => In Progress

** Changed in: intel-microcode (Ubuntu Focal)
       Status: New => In Progress

** Changed in: intel-microcode (Ubuntu Eoan)
       Status: New => In Progress

** Information type changed from Public to Public Security

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https://bugs.launchpad.net/bugs/1883016

Title:
  revert tmpfiles.d loading of microcode

Status in intel-microcode package in Ubuntu:
  In Progress
Status in intel-microcode source package in Eoan:
  In Progress
Status in intel-microcode source package in Focal:
  In Progress
Status in intel-microcode source package in Groovy:
  In Progress

Bug description:
  [Impact]

  revert tmpfiles.d loading of microcode

  Sometimes, despite intensive testing bad microcode can be shipped.

  When bad microcode is shipped and it is attempted to be loaded at
  package configuration time, system will end up in inconsistent state.
  Specifically apt transaction is aborted, new microcode is unpacked on
  disk but dpkg database is in inconsistent state.

  Thus whilst it was meant to be a canary, it wasn't a good one. Also it
  applies on initrd-less boot, initrd-full boot, early initrd and
  package upgrades. Which is not the right design here.

  Ideally, installing microcode update would generate a one time boot
  option to try new microcode, if successful commit booting with it.
  Otherwise fallback to previous version of the microcode. None of that
  is solvable with tmpfiles however.

  Most recent examples is the Skylake regression on 0x000406e3 systems

  https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1882890
  https://bugs.launchpad.net/ubuntu/+source/intel-microcode/+bug/1883002

  [Test Case]

   * downgrade to old intel-microcode package
   * reboot
   * upgrade to new intel-microcode package
   * observe that uncoordinate microcode update is not attempted at package configuration time

  [Regression Potential]

   * This is a revert

  [Other Info]
   
   * microcode try, commit or revert would be nice to implement.

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