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linux-next/arch/x86/kvm/mtrr.c
Marios Pomonis 25a5edea71 KVM: x86: Protect MSR-based index computations in fixed_msr_to_seg_unit() from Spectre-v1/L1TF attacks
This fixes a Spectre-v1/L1TF vulnerability in fixed_msr_to_seg_unit().
This function contains index computations based on the
(attacker-controlled) MSR number.

Fixes: de9aef5e1a ("KVM: MTRR: introduce fixed_mtrr_segment table")

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>
2020-01-27 19:59:39 +01:00

726 lines
16 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/*
* vMTRR implementation
*
* Copyright (C) 2006 Qumranet, Inc.
* Copyright 2010 Red Hat, Inc. and/or its affiliates.
* Copyright(C) 2015 Intel Corporation.
*
* Authors:
* Yaniv Kamay <yaniv@qumranet.com>
* Avi Kivity <avi@qumranet.com>
* Marcelo Tosatti <mtosatti@redhat.com>
* Paolo Bonzini <pbonzini@redhat.com>
* Xiao Guangrong <guangrong.xiao@linux.intel.com>
*/
#include <linux/kvm_host.h>
#include <asm/mtrr.h>
#include "cpuid.h"
#include "mmu.h"
#define IA32_MTRR_DEF_TYPE_E (1ULL << 11)
#define IA32_MTRR_DEF_TYPE_FE (1ULL << 10)
#define IA32_MTRR_DEF_TYPE_TYPE_MASK (0xff)
static bool msr_mtrr_valid(unsigned msr)
{
switch (msr) {
case 0x200 ... 0x200 + 2 * KVM_NR_VAR_MTRR - 1:
case MSR_MTRRfix64K_00000:
case MSR_MTRRfix16K_80000:
case MSR_MTRRfix16K_A0000:
case MSR_MTRRfix4K_C0000:
case MSR_MTRRfix4K_C8000:
case MSR_MTRRfix4K_D0000:
case MSR_MTRRfix4K_D8000:
case MSR_MTRRfix4K_E0000:
case MSR_MTRRfix4K_E8000:
case MSR_MTRRfix4K_F0000:
case MSR_MTRRfix4K_F8000:
case MSR_MTRRdefType:
case MSR_IA32_CR_PAT:
return true;
}
return false;
}
static bool valid_mtrr_type(unsigned t)
{
return t < 8 && (1 << t) & 0x73; /* 0, 1, 4, 5, 6 */
}
bool kvm_mtrr_valid(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
int i;
u64 mask;
if (!msr_mtrr_valid(msr))
return false;
if (msr == MSR_IA32_CR_PAT) {
return kvm_pat_valid(data);
} else if (msr == MSR_MTRRdefType) {
if (data & ~0xcff)
return false;
return valid_mtrr_type(data & 0xff);
} else if (msr >= MSR_MTRRfix64K_00000 && msr <= MSR_MTRRfix4K_F8000) {
for (i = 0; i < 8 ; i++)
if (!valid_mtrr_type((data >> (i * 8)) & 0xff))
return false;
return true;
}
/* variable MTRRs */
WARN_ON(!(msr >= 0x200 && msr < 0x200 + 2 * KVM_NR_VAR_MTRR));
mask = (~0ULL) << cpuid_maxphyaddr(vcpu);
if ((msr & 1) == 0) {
/* MTRR base */
if (!valid_mtrr_type(data & 0xff))
return false;
mask |= 0xf00;
} else
/* MTRR mask */
mask |= 0x7ff;
if (data & mask) {
kvm_inject_gp(vcpu, 0);
return false;
}
return true;
}
EXPORT_SYMBOL_GPL(kvm_mtrr_valid);
static bool mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
{
return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_E);
}
static bool fixed_mtrr_is_enabled(struct kvm_mtrr *mtrr_state)
{
return !!(mtrr_state->deftype & IA32_MTRR_DEF_TYPE_FE);
}
static u8 mtrr_default_type(struct kvm_mtrr *mtrr_state)
{
return mtrr_state->deftype & IA32_MTRR_DEF_TYPE_TYPE_MASK;
}
static u8 mtrr_disabled_type(struct kvm_vcpu *vcpu)
{
/*
* Intel SDM 11.11.2.2: all MTRRs are disabled when
* IA32_MTRR_DEF_TYPE.E bit is cleared, and the UC
* memory type is applied to all of physical memory.
*
* However, virtual machines can be run with CPUID such that
* there are no MTRRs. In that case, the firmware will never
* enable MTRRs and it is obviously undesirable to run the
* guest entirely with UC memory and we use WB.
*/
if (guest_cpuid_has(vcpu, X86_FEATURE_MTRR))
return MTRR_TYPE_UNCACHABLE;
else
return MTRR_TYPE_WRBACK;
}
/*
* Three terms are used in the following code:
* - segment, it indicates the address segments covered by fixed MTRRs.
* - unit, it corresponds to the MSR entry in the segment.
* - range, a range is covered in one memory cache type.
*/
struct fixed_mtrr_segment {
u64 start;
u64 end;
int range_shift;
/* the start position in kvm_mtrr.fixed_ranges[]. */
int range_start;
};
static struct fixed_mtrr_segment fixed_seg_table[] = {
/* MSR_MTRRfix64K_00000, 1 unit. 64K fixed mtrr. */
{
.start = 0x0,
.end = 0x80000,
.range_shift = 16, /* 64K */
.range_start = 0,
},
/*
* MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000, 2 units,
* 16K fixed mtrr.
*/
{
.start = 0x80000,
.end = 0xc0000,
.range_shift = 14, /* 16K */
.range_start = 8,
},
/*
* MSR_MTRRfix4K_C0000 ... MSR_MTRRfix4K_F8000, 8 units,
* 4K fixed mtrr.
*/
{
.start = 0xc0000,
.end = 0x100000,
.range_shift = 12, /* 12K */
.range_start = 24,
}
};
/*
* The size of unit is covered in one MSR, one MSR entry contains
* 8 ranges so that unit size is always 8 * 2^range_shift.
*/
static u64 fixed_mtrr_seg_unit_size(int seg)
{
return 8 << fixed_seg_table[seg].range_shift;
}
static bool fixed_msr_to_seg_unit(u32 msr, int *seg, int *unit)
{
switch (msr) {
case MSR_MTRRfix64K_00000:
*seg = 0;
*unit = 0;
break;
case MSR_MTRRfix16K_80000 ... MSR_MTRRfix16K_A0000:
*seg = 1;
*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 = array_index_nospec(
msr - MSR_MTRRfix4K_C0000,
MSR_MTRRfix4K_F8000 - MSR_MTRRfix4K_C0000 + 1);
break;
default:
return false;
}
return true;
}
static void fixed_mtrr_seg_unit_range(int seg, int unit, u64 *start, u64 *end)
{
struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
u64 unit_size = fixed_mtrr_seg_unit_size(seg);
*start = mtrr_seg->start + unit * unit_size;
*end = *start + unit_size;
WARN_ON(*end > mtrr_seg->end);
}
static int fixed_mtrr_seg_unit_range_index(int seg, int unit)
{
struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
WARN_ON(mtrr_seg->start + unit * fixed_mtrr_seg_unit_size(seg)
> mtrr_seg->end);
/* each unit has 8 ranges. */
return mtrr_seg->range_start + 8 * unit;
}
static int fixed_mtrr_seg_end_range_index(int seg)
{
struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
int n;
n = (mtrr_seg->end - mtrr_seg->start) >> mtrr_seg->range_shift;
return mtrr_seg->range_start + n - 1;
}
static bool fixed_msr_to_range(u32 msr, u64 *start, u64 *end)
{
int seg, unit;
if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
return false;
fixed_mtrr_seg_unit_range(seg, unit, start, end);
return true;
}
static int fixed_msr_to_range_index(u32 msr)
{
int seg, unit;
if (!fixed_msr_to_seg_unit(msr, &seg, &unit))
return -1;
return fixed_mtrr_seg_unit_range_index(seg, unit);
}
static int fixed_mtrr_addr_to_seg(u64 addr)
{
struct fixed_mtrr_segment *mtrr_seg;
int seg, seg_num = ARRAY_SIZE(fixed_seg_table);
for (seg = 0; seg < seg_num; seg++) {
mtrr_seg = &fixed_seg_table[seg];
if (mtrr_seg->start <= addr && addr < mtrr_seg->end)
return seg;
}
return -1;
}
static int fixed_mtrr_addr_seg_to_range_index(u64 addr, int seg)
{
struct fixed_mtrr_segment *mtrr_seg;
int index;
mtrr_seg = &fixed_seg_table[seg];
index = mtrr_seg->range_start;
index += (addr - mtrr_seg->start) >> mtrr_seg->range_shift;
return index;
}
static u64 fixed_mtrr_range_end_addr(int seg, int index)
{
struct fixed_mtrr_segment *mtrr_seg = &fixed_seg_table[seg];
int pos = index - mtrr_seg->range_start;
return mtrr_seg->start + ((pos + 1) << mtrr_seg->range_shift);
}
static void var_mtrr_range(struct kvm_mtrr_range *range, u64 *start, u64 *end)
{
u64 mask;
*start = range->base & PAGE_MASK;
mask = range->mask & PAGE_MASK;
/* This cannot overflow because writing to the reserved bits of
* variable MTRRs causes a #GP.
*/
*end = (*start | ~mask) + 1;
}
static void update_mtrr(struct kvm_vcpu *vcpu, u32 msr)
{
struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
gfn_t start, end;
int index;
if (msr == MSR_IA32_CR_PAT || !tdp_enabled ||
!kvm_arch_has_noncoherent_dma(vcpu->kvm))
return;
if (!mtrr_is_enabled(mtrr_state) && msr != MSR_MTRRdefType)
return;
/* fixed MTRRs. */
if (fixed_msr_to_range(msr, &start, &end)) {
if (!fixed_mtrr_is_enabled(mtrr_state))
return;
} else if (msr == MSR_MTRRdefType) {
start = 0x0;
end = ~0ULL;
} else {
/* variable range MTRRs. */
index = (msr - 0x200) / 2;
var_mtrr_range(&mtrr_state->var_ranges[index], &start, &end);
}
kvm_zap_gfn_range(vcpu->kvm, gpa_to_gfn(start), gpa_to_gfn(end));
}
static bool var_mtrr_range_is_valid(struct kvm_mtrr_range *range)
{
return (range->mask & (1 << 11)) != 0;
}
static void set_var_mtrr_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
struct kvm_mtrr_range *tmp, *cur;
int index, is_mtrr_mask;
index = (msr - 0x200) / 2;
is_mtrr_mask = msr - 0x200 - 2 * index;
cur = &mtrr_state->var_ranges[index];
/* remove the entry if it's in the list. */
if (var_mtrr_range_is_valid(cur))
list_del(&mtrr_state->var_ranges[index].node);
/* Extend the mask with all 1 bits to the left, since those
* bits must implicitly be 0. The bits are then cleared
* when reading them.
*/
if (!is_mtrr_mask)
cur->base = data;
else
cur->mask = data | (-1LL << cpuid_maxphyaddr(vcpu));
/* add it to the list if it's enabled. */
if (var_mtrr_range_is_valid(cur)) {
list_for_each_entry(tmp, &mtrr_state->head, node)
if (cur->base >= tmp->base)
break;
list_add_tail(&cur->node, &tmp->node);
}
}
int kvm_mtrr_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data)
{
int index;
if (!kvm_mtrr_valid(vcpu, msr, data))
return 1;
index = fixed_msr_to_range_index(msr);
if (index >= 0)
*(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index] = data;
else if (msr == MSR_MTRRdefType)
vcpu->arch.mtrr_state.deftype = data;
else if (msr == MSR_IA32_CR_PAT)
vcpu->arch.pat = data;
else
set_var_mtrr_msr(vcpu, msr, data);
update_mtrr(vcpu, msr);
return 0;
}
int kvm_mtrr_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata)
{
int index;
/* MSR_MTRRcap is a readonly MSR. */
if (msr == MSR_MTRRcap) {
/*
* SMRR = 0
* WC = 1
* FIX = 1
* VCNT = KVM_NR_VAR_MTRR
*/
*pdata = 0x500 | KVM_NR_VAR_MTRR;
return 0;
}
if (!msr_mtrr_valid(msr))
return 1;
index = fixed_msr_to_range_index(msr);
if (index >= 0)
*pdata = *(u64 *)&vcpu->arch.mtrr_state.fixed_ranges[index];
else if (msr == MSR_MTRRdefType)
*pdata = vcpu->arch.mtrr_state.deftype;
else if (msr == MSR_IA32_CR_PAT)
*pdata = vcpu->arch.pat;
else { /* Variable MTRRs */
int is_mtrr_mask;
index = (msr - 0x200) / 2;
is_mtrr_mask = msr - 0x200 - 2 * index;
if (!is_mtrr_mask)
*pdata = vcpu->arch.mtrr_state.var_ranges[index].base;
else
*pdata = vcpu->arch.mtrr_state.var_ranges[index].mask;
*pdata &= (1ULL << cpuid_maxphyaddr(vcpu)) - 1;
}
return 0;
}
void kvm_vcpu_mtrr_init(struct kvm_vcpu *vcpu)
{
INIT_LIST_HEAD(&vcpu->arch.mtrr_state.head);
}
struct mtrr_iter {
/* input fields. */
struct kvm_mtrr *mtrr_state;
u64 start;
u64 end;
/* output fields. */
int mem_type;
/* mtrr is completely disabled? */
bool mtrr_disabled;
/* [start, end) is not fully covered in MTRRs? */
bool partial_map;
/* private fields. */
union {
/* used for fixed MTRRs. */
struct {
int index;
int seg;
};
/* used for var MTRRs. */
struct {
struct kvm_mtrr_range *range;
/* max address has been covered in var MTRRs. */
u64 start_max;
};
};
bool fixed;
};
static bool mtrr_lookup_fixed_start(struct mtrr_iter *iter)
{
int seg, index;
if (!fixed_mtrr_is_enabled(iter->mtrr_state))
return false;
seg = fixed_mtrr_addr_to_seg(iter->start);
if (seg < 0)
return false;
iter->fixed = true;
index = fixed_mtrr_addr_seg_to_range_index(iter->start, seg);
iter->index = index;
iter->seg = seg;
return true;
}
static bool match_var_range(struct mtrr_iter *iter,
struct kvm_mtrr_range *range)
{
u64 start, end;
var_mtrr_range(range, &start, &end);
if (!(start >= iter->end || end <= iter->start)) {
iter->range = range;
/*
* the function is called when we do kvm_mtrr.head walking.
* Range has the minimum base address which interleaves
* [looker->start_max, looker->end).
*/
iter->partial_map |= iter->start_max < start;
/* update the max address has been covered. */
iter->start_max = max(iter->start_max, end);
return true;
}
return false;
}
static void __mtrr_lookup_var_next(struct mtrr_iter *iter)
{
struct kvm_mtrr *mtrr_state = iter->mtrr_state;
list_for_each_entry_continue(iter->range, &mtrr_state->head, node)
if (match_var_range(iter, iter->range))
return;
iter->range = NULL;
iter->partial_map |= iter->start_max < iter->end;
}
static void mtrr_lookup_var_start(struct mtrr_iter *iter)
{
struct kvm_mtrr *mtrr_state = iter->mtrr_state;
iter->fixed = false;
iter->start_max = iter->start;
iter->range = NULL;
iter->range = list_prepare_entry(iter->range, &mtrr_state->head, node);
__mtrr_lookup_var_next(iter);
}
static void mtrr_lookup_fixed_next(struct mtrr_iter *iter)
{
/* terminate the lookup. */
if (fixed_mtrr_range_end_addr(iter->seg, iter->index) >= iter->end) {
iter->fixed = false;
iter->range = NULL;
return;
}
iter->index++;
/* have looked up for all fixed MTRRs. */
if (iter->index >= ARRAY_SIZE(iter->mtrr_state->fixed_ranges))
return mtrr_lookup_var_start(iter);
/* switch to next segment. */
if (iter->index > fixed_mtrr_seg_end_range_index(iter->seg))
iter->seg++;
}
static void mtrr_lookup_var_next(struct mtrr_iter *iter)
{
__mtrr_lookup_var_next(iter);
}
static void mtrr_lookup_start(struct mtrr_iter *iter)
{
if (!mtrr_is_enabled(iter->mtrr_state)) {
iter->mtrr_disabled = true;
return;
}
if (!mtrr_lookup_fixed_start(iter))
mtrr_lookup_var_start(iter);
}
static void mtrr_lookup_init(struct mtrr_iter *iter,
struct kvm_mtrr *mtrr_state, u64 start, u64 end)
{
iter->mtrr_state = mtrr_state;
iter->start = start;
iter->end = end;
iter->mtrr_disabled = false;
iter->partial_map = false;
iter->fixed = false;
iter->range = NULL;
mtrr_lookup_start(iter);
}
static bool mtrr_lookup_okay(struct mtrr_iter *iter)
{
if (iter->fixed) {
iter->mem_type = iter->mtrr_state->fixed_ranges[iter->index];
return true;
}
if (iter->range) {
iter->mem_type = iter->range->base & 0xff;
return true;
}
return false;
}
static void mtrr_lookup_next(struct mtrr_iter *iter)
{
if (iter->fixed)
mtrr_lookup_fixed_next(iter);
else
mtrr_lookup_var_next(iter);
}
#define mtrr_for_each_mem_type(_iter_, _mtrr_, _gpa_start_, _gpa_end_) \
for (mtrr_lookup_init(_iter_, _mtrr_, _gpa_start_, _gpa_end_); \
mtrr_lookup_okay(_iter_); mtrr_lookup_next(_iter_))
u8 kvm_mtrr_get_guest_memory_type(struct kvm_vcpu *vcpu, gfn_t gfn)
{
struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
struct mtrr_iter iter;
u64 start, end;
int type = -1;
const int wt_wb_mask = (1 << MTRR_TYPE_WRBACK)
| (1 << MTRR_TYPE_WRTHROUGH);
start = gfn_to_gpa(gfn);
end = start + PAGE_SIZE;
mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
int curr_type = iter.mem_type;
/*
* Please refer to Intel SDM Volume 3: 11.11.4.1 MTRR
* Precedences.
*/
if (type == -1) {
type = curr_type;
continue;
}
/*
* If two or more variable memory ranges match and the
* memory types are identical, then that memory type is
* used.
*/
if (type == curr_type)
continue;
/*
* If two or more variable memory ranges match and one of
* the memory types is UC, the UC memory type used.
*/
if (curr_type == MTRR_TYPE_UNCACHABLE)
return MTRR_TYPE_UNCACHABLE;
/*
* If two or more variable memory ranges match and the
* memory types are WT and WB, the WT memory type is used.
*/
if (((1 << type) & wt_wb_mask) &&
((1 << curr_type) & wt_wb_mask)) {
type = MTRR_TYPE_WRTHROUGH;
continue;
}
/*
* For overlaps not defined by the above rules, processor
* behavior is undefined.
*/
/* We use WB for this undefined behavior. :( */
return MTRR_TYPE_WRBACK;
}
if (iter.mtrr_disabled)
return mtrr_disabled_type(vcpu);
/* not contained in any MTRRs. */
if (type == -1)
return mtrr_default_type(mtrr_state);
/*
* We just check one page, partially covered by MTRRs is
* impossible.
*/
WARN_ON(iter.partial_map);
return type;
}
EXPORT_SYMBOL_GPL(kvm_mtrr_get_guest_memory_type);
bool kvm_mtrr_check_gfn_range_consistency(struct kvm_vcpu *vcpu, gfn_t gfn,
int page_num)
{
struct kvm_mtrr *mtrr_state = &vcpu->arch.mtrr_state;
struct mtrr_iter iter;
u64 start, end;
int type = -1;
start = gfn_to_gpa(gfn);
end = gfn_to_gpa(gfn + page_num);
mtrr_for_each_mem_type(&iter, mtrr_state, start, end) {
if (type == -1) {
type = iter.mem_type;
continue;
}
if (type != iter.mem_type)
return false;
}
if (iter.mtrr_disabled)
return true;
if (!iter.partial_map)
return true;
if (type == -1)
return true;
return type == mtrr_default_type(mtrr_state);
}