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KVM: x86: Protect MSR-based index computations from Spectre-v1/L1TF attacks in x86.c 

commit 6ec4c5eee1 upstream.

This fixes a Spectre-v1/L1TF vulnerability in set_msr_mce() and
get_msr_mce().
Both functions contain index computations based on the
(attacker-controlled) MSR number.

Fixes: 890ca9aefa ("KVM: Add MCE support")

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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Marios Pomonis 2019-12-11 12:47:49 -08:00 committed by Greg Kroah-Hartman
parent a07fdd5fcb
commit f2a5143182
1 changed files with 8 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

10
arch/x86/kvm/x86.c
View File

@ -2494,7 +2494,10 @@ static int set_msr_mce(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
default:
if (msr >= MSR_IA32_MC0_CTL &&
msr < MSR_IA32_MCx_CTL(bank_num)) {
u32 offset = msr - MSR_IA32_MC0_CTL;
u32 offset = array_index_nospec(
msr - MSR_IA32_MC0_CTL,
MSR_IA32_MCx_CTL(bank_num) - MSR_IA32_MC0_CTL);
/* only 0 or all 1s can be written to IA32_MCi_CTL
* some Linux kernels though clear bit 10 in bank 4 to
* workaround a BIOS/GART TBL issue on AMD K8s, ignore
@ -2921,7 +2924,10 @@ static int get_msr_mce(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata, bool host)
default:
if (msr >= MSR_IA32_MC0_CTL &&
msr < MSR_IA32_MCx_CTL(bank_num)) {
u32 offset = msr - MSR_IA32_MC0_CTL;
u32 offset = array_index_nospec(
msr - MSR_IA32_MC0_CTL,
MSR_IA32_MCx_CTL(bank_num) - MSR_IA32_MC0_CTL);
data = vcpu->arch.mce_banks[offset];
break;
}