[SRU][Trusty][PULL v2] Prevent speculation on user controlled pointer (LP: #1775137)

[Juerg Haefliger]

BugLink: https://bugs.launchpad.net/bugs/1775137

== SRU Justification ==
Upstream's Spectre v1 mitigation prevents speculation on a user controlled pointer. This part of the Spectre v1 patchset was never backported to 4.4 (for unknown reasons) so Xenial/Trusty/Precise are lacking it as well. All the other stable upstream kernels include it, so add it to our older kernels.

== Fix ==
Backport the following patches:
x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec
x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec

== Regression Potential ==
Low. Patches have been in upstream (and other distro kernels) for quite a while now and the changes only introduce a barrier on copy_from_user operations.

== Test Case ==
TBD.

v1 -> v2:
  - No functional changes.
  - Pulled backports/cherry-picks from upstream stable and tagged them
    accordingly.
  - Added a newline before my sign-off to start a new section.

Signed-off-by: Juerg Haefliger <juergh at canonical.com>
---

The following changes since commit 2dd022222443a00e54f58f0e2a0e5f9e78c0e6b7:

  UBUNTU: SAUCE: Rename osb() to barrier_nospec() (2018-07-26 09:46:02 +0200)

are available in the Git repository at:

  git://git.launchpad.net/~juergh/+git/trusty-linux lp1775137-v2

for you to fetch changes up to 7803ab83a55eb1e01f902e260f61a1526ab36a5f:

  x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec (2018-07-26 11:38:40 +0200)

----------------------------------------------------------------
Dan Williams (3):
      x86: Introduce __uaccess_begin_nospec() and uaccess_try_nospec
      x86/usercopy: Replace open coded stac/clac with __uaccess_{begin, end}
      x86/uaccess: Use __uaccess_begin_nospec() and uaccess_try_nospec

Linus Torvalds (2):
      x86: reorganize SMAP handling in user space accesses
      x86: fix SMAP in 32-bit environments

 arch/x86/include/asm/uaccess.h    | 47 +++++++++++++++-----
 arch/x86/include/asm/uaccess_32.h | 24 ++++++++++
 arch/x86/include/asm/uaccess_64.h | 94 +++++++++++++++++++++++++++------------
 arch/x86/lib/usercopy_32.c        | 20 ++++-----
 4 files changed, 136 insertions(+), 49 deletions(-)