linux-kernel - [PATCH 2/2] KVM: arm64: Substitute RANDOMIZE_BASE for HARDEN_EL2

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Message-Id: <20200721094445.82184-3-dbrazdil@google.com>
Date:   Tue, 21 Jul 2020 10:44:45 +0100
From:   David Brazdil <dbrazdil@...gle.com>
To:     Marc Zyngier <maz@...nel.org>, Will Deacon <will@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>,
        Julien Thierry <julien.thierry.kdev@...il.com>,
        Suzuki K Poulose <suzuki.poulose@....com>
Cc:     kvmarm@...ts.cs.columbia.edu, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org, android-kvm@...gle.com,
        kernel-team@...roid.com, David Brazdil <dbrazdil@...gle.com>
Subject: [PATCH 2/2] KVM: arm64: Substitute RANDOMIZE_BASE for HARDEN_EL2_VECTORS

The HARDEN_EL2_VECTORS config maps vectors at a fixed location on cores which
are susceptible to Spector variant 3a (A57, A72) to prevent defeating hyp
layout randomization by leaking the value of VBAR_EL2.

Since this feature is only applicable when EL2 layout randomization is enabled,
unify both behind the same RANDOMIZE_BASE Kconfig. Majority of code remains
conditional on a capability selected for the affected cores.

Signed-off-by: David Brazdil <dbrazdil@...gle.com>
---
 arch/arm64/Kconfig             | 16 ----------------
 arch/arm64/include/asm/mmu.h   |  6 ++----
 arch/arm64/kernel/cpu_errata.c |  4 ++--
 arch/arm64/kvm/Kconfig         |  2 +-
 4 files changed, 5 insertions(+), 23 deletions(-)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 66dc41fd49f2..527d217baf55 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1182,22 +1182,6 @@ config HARDEN_BRANCH_PREDICTOR
 
 	  If unsure, say Y.
 
-config HARDEN_EL2_VECTORS
-	bool "Harden EL2 vector mapping against system register leak" if EXPERT
-	default y
-	help
-	  Speculation attacks against some high-performance processors can
-	  be used to leak privileged information such as the vector base
-	  register, resulting in a potential defeat of the EL2 layout
-	  randomization.
-
-	  This config option will map the vectors to a fixed location,
-	  independent of the EL2 code mapping, so that revealing VBAR_EL2
-	  to an attacker does not give away any extra information. This
-	  only gets enabled on affected CPUs.
-
-	  If unsure, say Y.
-
 config ARM64_SSBD
 	bool "Speculative Store Bypass Disable" if EXPERT
 	default y
diff --git a/arch/arm64/include/asm/mmu.h b/arch/arm64/include/asm/mmu.h
index 8444df000181..e26542c0e79e 100644
--- a/arch/arm64/include/asm/mmu.h
+++ b/arch/arm64/include/asm/mmu.h
@@ -45,12 +45,10 @@ struct bp_hardening_data {
 	bp_hardening_cb_t	fn;
 };
 
-#if (defined(CONFIG_HARDEN_BRANCH_PREDICTOR) ||	\
-     defined(CONFIG_HARDEN_EL2_VECTORS))
-
+#ifdef CONFIG_KVM_INDIRECT_VECTORS
 extern char __bp_harden_hyp_vecs[];
 extern atomic_t arm64_el2_vector_last_slot;
-#endif  /* CONFIG_HARDEN_BRANCH_PREDICTOR || CONFIG_HARDEN_EL2_VECTORS */
+#endif
 
 #ifdef CONFIG_HARDEN_BRANCH_PREDICTOR
 DECLARE_PER_CPU_READ_MOSTLY(struct bp_hardening_data, bp_hardening_data);
diff --git a/arch/arm64/kernel/cpu_errata.c b/arch/arm64/kernel/cpu_errata.c
index 79728bfb5351..6bd1d3ad037a 100644
--- a/arch/arm64/kernel/cpu_errata.c
+++ b/arch/arm64/kernel/cpu_errata.c
@@ -632,7 +632,7 @@ has_neoverse_n1_erratum_1542419(const struct arm64_cpu_capabilities *entry,
 	return is_midr_in_range(midr, &range) && has_dic;
 }
 
-#if defined(CONFIG_HARDEN_EL2_VECTORS)
+#ifdef CONFIG_RANDOMIZE_BASE
 
 static const struct midr_range ca57_a72[] = {
 	MIDR_ALL_VERSIONS(MIDR_CORTEX_A57),
@@ -891,7 +891,7 @@ const struct arm64_cpu_capabilities arm64_errata[] = {
 		.type = ARM64_CPUCAP_LOCAL_CPU_ERRATUM,
 		.matches = check_branch_predictor,
 	},
-#ifdef CONFIG_HARDEN_EL2_VECTORS
+#ifdef CONFIG_RANDOMIZE_BASE
 	{
 		.desc = "EL2 vector hardening",
 		.capability = ARM64_HARDEN_EL2_VECTORS,
diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 13489aff4440..318c8f2df245 100644
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -58,7 +58,7 @@ config KVM_ARM_PMU
 	  virtual machines.
 
 config KVM_INDIRECT_VECTORS
-	def_bool HARDEN_BRANCH_PREDICTOR || HARDEN_EL2_VECTORS
+	def_bool HARDEN_BRANCH_PREDICTOR || RANDOMIZE_BASE
 
 endif # KVM
 
-- 
2.27.0