tree 9a294782b7d3d4fd3c48f16bf39d57b34be44ad1
parent 3494d58865ad4a47611dbb427b214cc5227fa5eb
parent da631f7fd623b6c180c8d93a93040d1e0d61291f
author Linus Torvalds <torvalds@linux-foundation.org> 1605814351 -0800
committer Linus Torvalds <torvalds@linux-foundation.org> 1605814351 -0800
mergetag object da631f7fd623b6c180c8d93a93040d1e0d61291f
 type commit
 tag powerpc-cve-2020-4788
 tagger Michael Ellerman <mpe@ellerman.id.au> 1605790369 +1100
 
 powerpc fixes for CVE-2020-4788
 
 From Daniel's cover letter:
 
 IBM Power9 processors can speculatively operate on data in the L1 cache
 before it has been completely validated, via a way-prediction mechanism. It
 is not possible for an attacker to determine the contents of impermissible
 memory using this method, since these systems implement a combination of
 hardware and software security measures to prevent scenarios where
 protected data could be leaked.
 
 However these measures don't address the scenario where an attacker induces
 the operating system to speculatively execute instructions using data that
 the attacker controls. This can be used for example to speculatively bypass
 "kernel user access prevention" techniques, as discovered by Anthony
 Steinhauser of Google's Safeside Project. This is not an attack by itself,
 but there is a possibility it could be used in conjunction with
 side-channels or other weaknesses in the privileged code to construct an
 attack.
 
 This issue can be mitigated by flushing the L1 cache between privilege
 boundaries of concern.
 
 This patch series flushes the L1 cache on kernel entry (patch 2) and after the
 kernel performs any user accesses (patch 3). It also adds a self-test and
 performs some related cleanups.
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Merge tag 'powerpc-cve-2020-4788' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux

Pull powerpc fixes from Michael Ellerman:
 "Fixes for CVE-2020-4788.

  From Daniel's cover letter:

  IBM Power9 processors can speculatively operate on data in the L1
  cache before it has been completely validated, via a way-prediction
  mechanism. It is not possible for an attacker to determine the
  contents of impermissible memory using this method, since these
  systems implement a combination of hardware and software security
  measures to prevent scenarios where protected data could be leaked.

  However these measures don't address the scenario where an attacker
  induces the operating system to speculatively execute instructions
  using data that the attacker controls. This can be used for example to
  speculatively bypass "kernel user access prevention" techniques, as
  discovered by Anthony Steinhauser of Google's Safeside Project. This
  is not an attack by itself, but there is a possibility it could be
  used in conjunction with side-channels or other weaknesses in the
  privileged code to construct an attack.

  This issue can be mitigated by flushing the L1 cache between privilege
  boundaries of concern.

  This patch series flushes the L1 cache on kernel entry (patch 2) and
  after the kernel performs any user accesses (patch 3). It also adds a
  self-test and performs some related cleanups"

* tag 'powerpc-cve-2020-4788' of git://git.kernel.org/pub/scm/linux/kernel/git/powerpc/linux:
  powerpc/64s: rename pnv|pseries_setup_rfi_flush to _setup_security_mitigations
  selftests/powerpc: refactor entry and rfi_flush tests
  selftests/powerpc: entry flush test
  powerpc: Only include kup-radix.h for 64-bit Book3S
  powerpc/64s: flush L1D after user accesses
  powerpc/64s: flush L1D on kernel entry
  selftests/powerpc: rfi_flush: disable entry flush if present