Commit ea740059 authored by Marios Pomonis's avatar Marios Pomonis Committed by Paolo Bonzini
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KVM: x86: Protect DR-based index computations from Spectre-v1/L1TF attacks 



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: 020df079 ("KVM: move DR register access handling into generic code")

Signed-off-by: default avatarNick Finco <nifi@google.com>
Signed-off-by: default avatarMarios Pomonis <pomonis@google.com>
Reviewed-by: default avatarAndrew Honig <ahonig@google.com>
Cc: stable@vger.kernel.org
Reviewed-by: default avatarJim Mattson <jmattson@google.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent c926f2f7

arch/x86/kvm/x86.c

+6 −2
Original line number Diff line number Diff line
@@ -1063,9 +1063,11 @@ 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;
@@ -1102,9 +1104,11 @@ 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 */