[PATCH] KVM: x86: Extend Spectre-v1 mitigation
From: Marios Pomonis
Date: Fri Nov 22 2019 - 13:41:05 EST
From: Nick Finco <nifi@xxxxxxxxxx>
This extends the Spectre-v1 mitigation introduced in
commit 75f139aaf896 ("KVM: x86: Add memory barrier on vmcs field lookup")
and commit 085331dfc6bb ("x86/kvm: Update spectre-v1 mitigation") in light
of the Spectre-v1/L1TF combination described here:
https://xenbits.xen.org/xsa/advisory-289.html
As reported in the link, an attacker can use the cache-load part of a
Spectre-v1 gadget to bring memory into the L1 cache, then use L1TF to
leak the loaded memory. Note that this attack is not fully mitigated by
core scheduling; an attacker could employ L1TF on the same thread that
loaded the memory in L1 instead of relying on neighboring hyperthreads.
This patch uses array_index_nospec() to prevent index computations from
causing speculative loads into the L1 cache. These cases involve a
bounds check followed by a memory read using the index; this is more
common than the full Spectre-v1 pattern. In some cases, the index
computation can be eliminated entirely by small amounts of refactoring.
Signed-off-by: Nick Finco <nifi@xxxxxxxxxx>
Signed-off-by: Marios Pomonis <pomonis@xxxxxxxxxx>
Acked-by: Andrew Honig <ahonig@xxxxxxxxxx>
---
arch/x86/kvm/emulate.c | 11 ++++++++---
arch/x86/kvm/hyperv.c | 10 ++++++----
arch/x86/kvm/i8259.c | 6 +++++-
arch/x86/kvm/ioapic.c | 15 +++++++++------
arch/x86/kvm/lapic.c | 13 +++++++++----
arch/x86/kvm/mtrr.c | 8 ++++++--
arch/x86/kvm/pmu.h | 18 ++++++++++++++----
arch/x86/kvm/vmx/pmu_intel.c | 24 ++++++++++++++++--------
arch/x86/kvm/vmx/vmx.c | 22 ++++++++++++++++------
arch/x86/kvm/x86.c | 18 ++++++++++++++----
10 files changed, 103 insertions(+), 42 deletions(-)
diff --git a/arch/x86/kvm/emulate.c b/arch/x86/kvm/emulate.c
index 952d1a4f4d7e..fcf7cdb21d60 100644
--- a/arch/x86/kvm/emulate.c
+++ b/arch/x86/kvm/emulate.c
@@ -5303,10 +5303,15 @@ int x86_decode_insn(struct x86_emulate_ctxt *ctxt, void *insn, int insn_len)
}
break;
case Escape:
- if (ctxt->modrm > 0xbf)
- opcode = opcode.u.esc->high[ctxt->modrm - 0xc0];
- else
+ if (ctxt->modrm > 0xbf) {
+ size_t size = ARRAY_SIZE(opcode.u.esc->high);
+ u32 index = array_index_nospec(
+ ctxt->modrm - 0xc0, size);
+
+ opcode = opcode.u.esc->high[index];
+ } else {
opcode = opcode.u.esc->op[(ctxt->modrm >> 3) & 7];
+ }
break;
case InstrDual:
if ((ctxt->modrm >> 6) == 3)
diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 23ff65504d7e..26408434b9bc 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -809,11 +809,12 @@ static int kvm_hv_msr_get_crash_data(struct kvm_vcpu *vcpu,
u32 index, u64 *pdata)
{
struct kvm_hv *hv = &vcpu->kvm->arch.hyperv;
+ size_t size = ARRAY_SIZE(hv->hv_crash_param);
- if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
+ if (WARN_ON_ONCE(index >= size))
return -EINVAL;
- *pdata = hv->hv_crash_param[index];
+ *pdata = hv->hv_crash_param[array_index_nospec(index, size)];
return 0;
}
@@ -852,11 +853,12 @@ static int kvm_hv_msr_set_crash_data(struct kvm_vcpu *vcpu,
u32 index, u64 data)
{
struct kvm_hv *hv = &vcpu->kvm->arch.hyperv;
+ size_t size = ARRAY_SIZE(hv->hv_crash_param);
- if (WARN_ON_ONCE(index >= ARRAY_SIZE(hv->hv_crash_param)))
+ if (WARN_ON_ONCE(index >= size))
return -EINVAL;
- hv->hv_crash_param[index] = data;
+ hv->hv_crash_param[array_index_nospec(index, size)] = data;
return 0;
}
diff --git a/arch/x86/kvm/i8259.c b/arch/x86/kvm/i8259.c
index 8b38bb4868a6..629a09ca9860 100644
--- a/arch/x86/kvm/i8259.c
+++ b/arch/x86/kvm/i8259.c
@@ -460,10 +460,14 @@ static int picdev_write(struct kvm_pic *s,
switch (addr) {
case 0x20:
case 0x21:
+ pic_lock(s);
+ pic_ioport_write(&s->pics[0], addr, data);
+ pic_unlock(s);
+ break;
case 0xa0:
case 0xa1:
pic_lock(s);
- pic_ioport_write(&s->pics[addr >> 7], addr, data);
+ pic_ioport_write(&s->pics[1], addr, data);
pic_unlock(s);
break;
case 0x4d0:
diff --git a/arch/x86/kvm/ioapic.c b/arch/x86/kvm/ioapic.c
index 9fd2dd89a1c5..8aa58727045e 100644
--- a/arch/x86/kvm/ioapic.c
+++ b/arch/x86/kvm/ioapic.c
@@ -36,6 +36,7 @@
#include <linux/io.h>
#include <linux/slab.h>
#include <linux/export.h>
+#include <linux/nospec.h>
#include <asm/processor.h>
#include <asm/page.h>
#include <asm/current.h>
@@ -68,13 +69,14 @@ static unsigned long ioapic_read_indirect(struct kvm_ioapic *ioapic,
default:
{
u32 redir_index = (ioapic->ioregsel - 0x10) >> 1;
- u64 redir_content;
+ u64 redir_content = ~0ULL;
- if (redir_index < IOAPIC_NUM_PINS)
- redir_content =
- ioapic->redirtbl[redir_index].bits;
- else
- redir_content = ~0ULL;
+ if (redir_index < IOAPIC_NUM_PINS) {
+ u32 index = array_index_nospec(
+ redir_index, IOAPIC_NUM_PINS);
+
+ redir_content = ioapic->redirtbl[index].bits;
+ }
result = (ioapic->ioregsel & 0x1) ?
(redir_content >> 32) & 0xffffffff :
@@ -292,6 +294,7 @@ static void ioapic_write_indirect(struct kvm_ioapic *ioapic, u32 val)
if (index >= IOAPIC_NUM_PINS)
return;
+ index = array_index_nospec(index, IOAPIC_NUM_PINS);
e = &ioapic->redirtbl[index];
mask_before = e->fields.mask;
/* Preserve read-only fields */
diff --git a/arch/x86/kvm/lapic.c b/arch/x86/kvm/lapic.c
index cf9177b4a07f..3323115f52d5 100644
--- a/arch/x86/kvm/lapic.c
+++ b/arch/x86/kvm/lapic.c
@@ -1963,15 +1963,20 @@ int kvm_lapic_reg_write(struct kvm_lapic *apic, u32 reg, u32 val)
case APIC_LVTTHMR:
case APIC_LVTPC:
case APIC_LVT1:
- case APIC_LVTERR:
+ case APIC_LVTERR: {
/* TODO: Check vector */
+ size_t size;
+ u32 index;
+
if (!kvm_apic_sw_enabled(apic))
val |= APIC_LVT_MASKED;
-
- val &= apic_lvt_mask[(reg - APIC_LVTT) >> 4];
+ size = ARRAY_SIZE(apic_lvt_mask);
+ index = array_index_nospec(
+ (reg - APIC_LVTT) >> 4, size);
+ val &= apic_lvt_mask[index];
kvm_lapic_set_reg(apic, reg, val);
-
break;
+ }
case APIC_LVTT:
if (!kvm_apic_sw_enabled(apic))
diff --git a/arch/x86/kvm/mtrr.c b/arch/x86/kvm/mtrr.c
index 25ce3edd1872..7f0059aa30e1 100644
--- a/arch/x86/kvm/mtrr.c
+++ b/arch/x86/kvm/mtrr.c
@@ -192,11 +192,15 @@ static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
break;
case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
*seg = 1;
- *unit = msr - MSR_MTRRfix16K_80000;
+ *unit = array_index_nospec(
+ msr - MSR_MTRRfix16K_80000,
+ MSR_MTRRfix16K_A0000 - MSR_MTRRfix16K_80000 + 1);
break;
case MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000:
*seg = 2;
- *unit = msr - MSR_MTRRfix4K_C0000;
+ *unit = array_index_nospec(
+ msr - MSR_MTRRfix4K_C0000,
+ MSR_MTRRfix4K_F8000 - MSR_MTRRfix4K_C0000 + 1);
break;
default:
return false;
diff --git a/arch/x86/kvm/pmu.h b/arch/x86/kvm/pmu.h
index 7ebb62326c14..13332984b6d5 100644
--- a/arch/x86/kvm/pmu.h
+++ b/arch/x86/kvm/pmu.h
@@ -2,6 +2,8 @@
#ifndef __KVM_X86_PMU_H
#define __KVM_X86_PMU_H
+#include <linux/nospec.h>
+
#define vcpu_to_pmu(vcpu) (&(vcpu)->arch.pmu)
#define pmu_to_vcpu(pmu) (container_of((pmu), struct kvm_vcpu, arch.pmu))
#define pmc_to_pmu(pmc) (&(pmc)->vcpu->arch.pmu)
@@ -102,8 +104,12 @@ static inline bool kvm_valid_perf_global_ctrl(struct kvm_pmu *pmu,
static inline struct kvm_pmc *get_gp_pmc(struct kvm_pmu *pmu, u32 msr,
u32 base)
{
- if (msr >= base && msr < base + pmu->nr_arch_gp_counters)
- return &pmu->gp_counters[msr - base];
+ if (msr >= base && msr < base + pmu->nr_arch_gp_counters) {
+ u32 index = array_index_nospec(msr - base,
+ pmu->nr_arch_gp_counters);
+
+ return &pmu->gp_counters[index];
+ }
return NULL;
}
@@ -113,8 +119,12 @@ static inline struct kvm_pmc *get_fixed_pmc(struct kvm_pmu *pmu, u32 msr)
{
int base = MSR_CORE_PERF_FIXED_CTR0;
- if (msr >= base && msr < base + pmu->nr_arch_fixed_counters)
- return &pmu->fixed_counters[msr - base];
+ if (msr >= base && msr < base + pmu->nr_arch_fixed_counters) {
+ u32 index = array_index_nospec(msr - base,
+ pmu->nr_arch_fixed_counters);
+
+ return &pmu->fixed_counters[index];
+ }
return NULL;
}
diff --git a/arch/x86/kvm/vmx/pmu_intel.c b/arch/x86/kvm/vmx/pmu_intel.c
index 7023138b1cb0..34a3a17bb6d7 100644
--- a/arch/x86/kvm/vmx/pmu_intel.c
+++ b/arch/x86/kvm/vmx/pmu_intel.c
@@ -86,10 +86,14 @@ static unsigned intel_find_arch_event(struct kvm_pmu *pmu,
static unsigned intel_find_fixed_event(int idx)
{
- if (idx >= ARRAY_SIZE(fixed_pmc_events))
+ u32 event;
+ size_t size = ARRAY_SIZE(fixed_pmc_events);
+
+ if (idx >= size)
return PERF_COUNT_HW_MAX;
- return intel_arch_events[fixed_pmc_events[idx]].event_type;
+ event = fixed_pmc_events[array_index_nospec(idx, size)];
+ return intel_arch_events[event].event_type;
}
/* check if a PMC is enabled by comparing it with globl_ctrl bits. */
@@ -130,16 +134,20 @@ static struct kvm_pmc *intel_rdpmc_ecx_to_pmc(struct kvm_vcpu *vcpu,
struct kvm_pmu *pmu = vcpu_to_pmu(vcpu);
bool fixed = idx & (1u << 30);
struct kvm_pmc *counters;
+ unsigned int num_counters;
idx &= ~(3u << 30);
- if (!fixed && idx >= pmu->nr_arch_gp_counters)
- return NULL;
- if (fixed && idx >= pmu->nr_arch_fixed_counters)
+ if (fixed) {
+ counters = pmu->fixed_counters;
+ num_counters = pmu->nr_arch_fixed_counters;
+ } else {
+ counters = pmu->gp_counters;
+ num_counters = pmu->nr_arch_gp_counters;
+ }
+ if (idx >= num_counters)
return NULL;
- counters = fixed ? pmu->fixed_counters : pmu->gp_counters;
*mask &= pmu->counter_bitmask[fixed ? KVM_PMC_FIXED : KVM_PMC_GP];
-
- return &counters[idx];
+ return &counters[array_index_nospec(idx, num_counters)];
}
static bool intel_is_valid_msr(struct kvm_vcpu *vcpu, u32 msr)
diff --git a/arch/x86/kvm/vmx/vmx.c b/arch/x86/kvm/vmx/vmx.c
index d39475e2d44e..84def8e46d10 100644
--- a/arch/x86/kvm/vmx/vmx.c
+++ b/arch/x86/kvm/vmx/vmx.c
@@ -753,7 +753,9 @@ static bool vmx_segment_cache_test_set(struct vcpu_vmx *vmx, unsigned seg,
static u16 vmx_read_guest_seg_selector(struct vcpu_vmx *vmx, unsigned seg)
{
- u16 *p = &vmx->segment_cache.seg[seg].selector;
+ size_t size = ARRAY_SIZE(vmx->segment_cache.seg);
+ size_t index = array_index_nospec(seg, size);
+ u16 *p = &vmx->segment_cache.seg[index].selector;
if (!vmx_segment_cache_test_set(vmx, seg, SEG_FIELD_SEL))
*p = vmcs_read16(kvm_vmx_segment_fields[seg].selector);
@@ -762,7 +764,9 @@ static u16 vmx_read_guest_seg_selector(struct vcpu_vmx *vmx, unsigned seg)
static ulong vmx_read_guest_seg_base(struct vcpu_vmx *vmx, unsigned seg)
{
- ulong *p = &vmx->segment_cache.seg[seg].base;
+ size_t size = ARRAY_SIZE(vmx->segment_cache.seg);
+ size_t index = array_index_nospec(seg, size);
+ ulong *p = &vmx->segment_cache.seg[index].base;
if (!vmx_segment_cache_test_set(vmx, seg, SEG_FIELD_BASE))
*p = vmcs_readl(kvm_vmx_segment_fields[seg].base);
@@ -771,7 +775,9 @@ static ulong vmx_read_guest_seg_base(struct vcpu_vmx *vmx, unsigned seg)
static u32 vmx_read_guest_seg_limit(struct vcpu_vmx *vmx, unsigned seg)
{
- u32 *p = &vmx->segment_cache.seg[seg].limit;
+ size_t size = ARRAY_SIZE(vmx->segment_cache.seg);
+ size_t index = array_index_nospec(seg, size);
+ u32 *p = &vmx->segment_cache.seg[index].limit;
if (!vmx_segment_cache_test_set(vmx, seg, SEG_FIELD_LIMIT))
*p = vmcs_read32(kvm_vmx_segment_fields[seg].limit);
@@ -780,7 +786,9 @@ static u32 vmx_read_guest_seg_limit(struct vcpu_vmx *vmx, unsigned seg)
static u32 vmx_read_guest_seg_ar(struct vcpu_vmx *vmx, unsigned seg)
{
- u32 *p = &vmx->segment_cache.seg[seg].ar;
+ size_t size = ARRAY_SIZE(vmx->segment_cache.seg);
+ size_t index = array_index_nospec(seg, size);
+ u32 *p = &vmx->segment_cache.seg[index].ar;
if (!vmx_segment_cache_test_set(vmx, seg, SEG_FIELD_AR))
*p = vmcs_read32(kvm_vmx_segment_fields[seg].ar_bytes);
@@ -5828,6 +5836,8 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
{
struct vcpu_vmx *vmx = to_vmx(vcpu);
u32 exit_reason = vmx->exit_reason;
+ u32 bounded_exit_reason = array_index_nospec(exit_reason,
+ kvm_vmx_max_exit_handlers);
u32 vectoring_info = vmx->idt_vectoring_info;
trace_kvm_exit(exit_reason, vcpu, KVM_ISA_VMX);
@@ -5911,7 +5921,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
}
if (exit_reason < kvm_vmx_max_exit_handlers
- && kvm_vmx_exit_handlers[exit_reason]) {
+ && kvm_vmx_exit_handlers[bounded_exit_reason]) {
#ifdef CONFIG_RETPOLINE
if (exit_reason == EXIT_REASON_MSR_WRITE)
return kvm_emulate_wrmsr(vcpu);
@@ -5926,7 +5936,7 @@ static int vmx_handle_exit(struct kvm_vcpu *vcpu)
else if (exit_reason == EXIT_REASON_EPT_MISCONFIG)
return handle_ept_misconfig(vcpu);
#endif
- return kvm_vmx_exit_handlers[exit_reason](vcpu);
+ return kvm_vmx_exit_handlers[bounded_exit_reason](vcpu);
} else {
vcpu_unimpl(vcpu, "vmx: unexpected exit reason 0x%x\n",
exit_reason);
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index a256e09f321a..9a2789652231 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1057,9 +1057,11 @@ 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;
@@ -1096,9 +1098,11 @@ 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 */
@@ -2496,7 +2500,10 @@ 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
@@ -2937,7 +2944,10 @@ 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;
}
--
2.24.0.432.g9d3f5f5b63-goog