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[Bug 1774181] Re: Update to upstream's implementation of Spectre v1 mitigation

To: group.of.nepali.translators@xxxxxxxxxxxxxxxxxxx
From: Kleber Sacilotto de Souza <kleber.souza@xxxxxxxxxxxxx>
Date: Thu, 07 Jun 2018 16:46:02 -0000
Reply-to: Bug 1774181 <1774181@xxxxxxxxxxxxxxxxxx>
Sender: bounces@xxxxxxxxxxxxx

** Also affects: linux (Ubuntu Precise)
   Importance: Undecided
       Status: New

** Also affects: linux (Ubuntu Trusty)
   Importance: Undecided
       Status: New

** Also affects: linux (Ubuntu Xenial)
   Importance: Undecided
       Status: New

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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:
  New
Status in linux source package in Trusty:
  New
Status in linux source package in Xenial:
  New

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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