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

1 files changed, 7 insertions, 0 deletions

diff --git a/arch/powerpc/include/asm/security_features.h b/arch/powerpc/include/asm/security_features.h
index fbb8fa32150f..b774a4477d5f 100644
--- a/arch/powerpc/include/asm/security_features.h
+++ b/arch/powerpc/include/asm/security_features.h
@@ -86,12 +86,19 @@ static inline bool security_ftr_enabled(u64 feature)
 // Software required to flush link stack on context switch
 #define SEC_FTR_FLUSH_LINK_STACK	0x0000000000001000ull
 
+// The L1-D cache should be flushed when entering the kernel
+#define SEC_FTR_L1D_FLUSH_ENTRY		0x0000000000004000ull
+
+// The L1-D cache should be flushed after user accesses from the kernel
+#define SEC_FTR_L1D_FLUSH_UACCESS	0x0000000000008000ull
 
 // Features enabled by default
 #define SEC_FTR_DEFAULT \
 	(SEC_FTR_L1D_FLUSH_HV | \
 	 SEC_FTR_L1D_FLUSH_PR | \
 	 SEC_FTR_BNDS_CHK_SPEC_BAR | \
+	 SEC_FTR_L1D_FLUSH_ENTRY | \
+	 SEC_FTR_L1D_FLUSH_UACCESS | \
 	 SEC_FTR_FAVOUR_SECURITY)
 
 #endif /* _ASM_POWERPC_SECURITY_FEATURES_H */