Patch-mainline: v5.6-rc1

Git-commit: ea740059ecb37807ba47b84b33d1447435a8d868

From: Marios Pomonis <pomonis@google.com>

Date: Wed, 11 Dec 2019 12:47:52 -0800

Subject: [PATCH] KVM: x86: Protect DR-based index computations from

 Spectre-v1/L1TF attacks

References: bsc#1164734

This fixes a Spectre-v1/L1TF vulnerability in __kvm_set_dr() and

kvm_get_dr().

Both kvm_get_dr() and kvm_set_dr() (a wrapper of __kvm_set_dr()) are

exported symbols so KVM should tream them conservatively from a security

perspective.

Fixes: 020df0794f57 ("KVM: move DR register access handling into generic code")

Signed-off-by: Nick Finco <nifi@google.com>

Signed-off-by: Marios Pomonis <pomonis@google.com>

Reviewed-by: Andrew Honig <ahonig@google.com>

Cc: stable@vger.kernel.org

Reviewed-by: Jim Mattson <jmattson@google.com>

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

Signed-off-by: Juergen Gross <jgross@suse.com>

---

 arch/x86/kvm/x86.c | 8 ++++++--

 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c

index 913e55f6dca3..780224e76723 100644

--- a/arch/x86/kvm/x86.c

+++ b/arch/x86/kvm/x86.c

@@ -917,9 +917,11 @@ static u64 kvm_dr6_fixed(struct kvm_vcpu *vcpu)

 static int __kvm_set_dr(struct kvm_vcpu *vcpu, int dr, unsigned long val)

 {

+	size_t size = ARRAY_SIZE(vcpu->arch.db);

+

 	switch (dr) {

 	case 0 ... 3:

-		vcpu->arch.db[dr] = val;

+		vcpu->arch.db[array_index_nospec(dr, size)] = val;

 		if (!(vcpu->guest_debug & KVM_GUESTDBG_USE_HW_BP))

 			vcpu->arch.eff_db[dr] = val;

 		break;

@@ -956,9 +958,11 @@ EXPORT_SYMBOL_GPL(kvm_set_dr);

 int kvm_get_dr(struct kvm_vcpu *vcpu, int dr, unsigned long *val)

 {

+	size_t size = ARRAY_SIZE(vcpu->arch.db);

+

 	switch (dr) {

 	case 0 ... 3:

-		*val = vcpu->arch.db[dr];

+		*val = vcpu->arch.db[array_index_nospec(dr, size)];

 		break;

 	case 4:

 		/* fall through */

-- 

2.16.4