** Changed in: linux (Ubuntu Precise)
       Status: New => In Progress

** Changed in: linux (Ubuntu Precise)
     Assignee: (unassigned) => Juerg Haefliger (juergh)

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https://bugs.launchpad.net/bugs/1774181

Title:
  Update to upstream's implementation of Spectre v1 mitigation

Status in linux package in Ubuntu:
  Incomplete
Status in linux source package in Precise:
  In Progress
Status in linux source package in Trusty:
  Fix Released
Status in linux source package in Xenial:
  Fix Released

Bug description:
  Xenial/Trusty/Precise are currently lacking full support of upstream's
  Spectre v1 mitigation. Add the missing patches and merge them with
  Ubuntu's current implementation.

  == SRU Justification ==
  Ubuntu's Spectre v1 mitigation is based on the original embargoed patchset 
which introduced a barrier macro to prevent speculation beyond array boundaries 
for user controlled indices. What eventually landed in upstream is slightly 
different and uses a barrier macro in combination with a masking solution (plus 
syscall table and user pointer sanitation). During the updates to newer stable 
upstream versions, all those patches were skipped. After reviewing them, we 
want to bring them back and merge them with the current implementation which 
brings us back in sync with upstream stable.

  == Fix ==
  Add all the missing Spectre v1 patches from upstream stable 4.4.118 to 
4.4.131. Where appropriate, replace Ubuntu's additional barriers with the 
masking macro.

  == Regression Potential ==
  Low. The patches have been in upstream for quite a while now and we keep the 
speculation barriers that are currently in Ubuntu but not in upstream.

  == Test Case ==
  TBD.

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