162 lines
5.2 KiB
Diff
162 lines
5.2 KiB
Diff
From: Andy Honig <ahonig@google.com>
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Date: Wed, 20 Feb 2013 14:48:10 -0800
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Subject: KVM: x86: Convert MSR_KVM_SYSTEM_TIME to use gfn_to_hva_cache
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functions (CVE-2013-1797)
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commit 0b79459b482e85cb7426aa7da683a9f2c97aeae1 upstream.
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There is a potential use after free issue with the handling of
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MSR_KVM_SYSTEM_TIME. If the guest specifies a GPA in a movable or removable
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memory such as frame buffers then KVM might continue to write to that
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address even after it's removed via KVM_SET_USER_MEMORY_REGION. KVM pins
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the page in memory so it's unlikely to cause an issue, but if the user
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space component re-purposes the memory previously used for the guest, then
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the guest will be able to corrupt that memory.
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Tested: Tested against kvmclock unit test
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Signed-off-by: Andrew Honig <ahonig@google.com>
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Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
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---
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arch/x86/include/asm/kvm_host.h | 4 ++--
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arch/x86/kvm/x86.c | 47 +++++++++++++++++----------------------
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2 files changed, 22 insertions(+), 29 deletions(-)
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diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
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index 635a74d..4979778 100644
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--- a/arch/x86/include/asm/kvm_host.h
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+++ b/arch/x86/include/asm/kvm_host.h
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@@ -414,8 +414,8 @@ struct kvm_vcpu_arch {
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gpa_t time;
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struct pvclock_vcpu_time_info hv_clock;
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unsigned int hw_tsc_khz;
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- unsigned int time_offset;
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- struct page *time_page;
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+ struct gfn_to_hva_cache pv_time;
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+ bool pv_time_enabled;
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/* set guest stopped flag in pvclock flags field */
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bool pvclock_set_guest_stopped_request;
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diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
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index 2ade60c..f19ac0a 100644
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -1406,10 +1406,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
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unsigned long flags, this_tsc_khz;
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struct kvm_vcpu_arch *vcpu = &v->arch;
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struct kvm_arch *ka = &v->kvm->arch;
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- void *shared_kaddr;
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s64 kernel_ns, max_kernel_ns;
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u64 tsc_timestamp, host_tsc;
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- struct pvclock_vcpu_time_info *guest_hv_clock;
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+ struct pvclock_vcpu_time_info guest_hv_clock;
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u8 pvclock_flags;
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bool use_master_clock;
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@@ -1463,7 +1462,7 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
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local_irq_restore(flags);
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- if (!vcpu->time_page)
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+ if (!vcpu->pv_time_enabled)
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return 0;
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/*
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@@ -1525,12 +1524,12 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
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*/
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vcpu->hv_clock.version += 2;
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- shared_kaddr = kmap_atomic(vcpu->time_page);
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-
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- guest_hv_clock = shared_kaddr + vcpu->time_offset;
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+ if (unlikely(kvm_read_guest_cached(v->kvm, &vcpu->pv_time,
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+ &guest_hv_clock, sizeof(guest_hv_clock))))
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+ return 0;
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/* retain PVCLOCK_GUEST_STOPPED if set in guest copy */
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- pvclock_flags = (guest_hv_clock->flags & PVCLOCK_GUEST_STOPPED);
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+ pvclock_flags = (guest_hv_clock.flags & PVCLOCK_GUEST_STOPPED);
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if (vcpu->pvclock_set_guest_stopped_request) {
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pvclock_flags |= PVCLOCK_GUEST_STOPPED;
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@@ -1543,12 +1542,9 @@ static int kvm_guest_time_update(struct kvm_vcpu *v)
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vcpu->hv_clock.flags = pvclock_flags;
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- memcpy(shared_kaddr + vcpu->time_offset, &vcpu->hv_clock,
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- sizeof(vcpu->hv_clock));
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-
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- kunmap_atomic(shared_kaddr);
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-
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- mark_page_dirty(v->kvm, vcpu->time >> PAGE_SHIFT);
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+ kvm_write_guest_cached(v->kvm, &vcpu->pv_time,
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+ &vcpu->hv_clock,
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+ sizeof(vcpu->hv_clock));
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return 0;
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}
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@@ -1837,10 +1833,7 @@ static int kvm_pv_enable_async_pf(struct kvm_vcpu *vcpu, u64 data)
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static void kvmclock_reset(struct kvm_vcpu *vcpu)
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{
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- if (vcpu->arch.time_page) {
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- kvm_release_page_dirty(vcpu->arch.time_page);
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- vcpu->arch.time_page = NULL;
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- }
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+ vcpu->arch.pv_time_enabled = false;
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}
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static void accumulate_steal_time(struct kvm_vcpu *vcpu)
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@@ -1947,6 +1940,7 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
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break;
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case MSR_KVM_SYSTEM_TIME_NEW:
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case MSR_KVM_SYSTEM_TIME: {
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+ u64 gpa_offset;
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kvmclock_reset(vcpu);
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vcpu->arch.time = data;
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@@ -1956,19 +1950,17 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info)
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if (!(data & 1))
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break;
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- /* ...but clean it before doing the actual write */
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- vcpu->arch.time_offset = data & ~(PAGE_MASK | 1);
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+ gpa_offset = data & ~(PAGE_MASK | 1);
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/* Check that the address is 32-byte aligned. */
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- if (vcpu->arch.time_offset &
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- (sizeof(struct pvclock_vcpu_time_info) - 1))
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+ if (gpa_offset & (sizeof(struct pvclock_vcpu_time_info) - 1))
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break;
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- vcpu->arch.time_page =
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- gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT);
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-
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- if (is_error_page(vcpu->arch.time_page))
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- vcpu->arch.time_page = NULL;
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+ if (kvm_gfn_to_hva_cache_init(vcpu->kvm,
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+ &vcpu->arch.pv_time, data & ~1ULL))
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+ vcpu->arch.pv_time_enabled = false;
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+ else
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+ vcpu->arch.pv_time_enabled = true;
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break;
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}
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@@ -2972,7 +2964,7 @@ static int kvm_vcpu_ioctl_x86_set_xcrs(struct kvm_vcpu *vcpu,
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*/
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static int kvm_set_guest_paused(struct kvm_vcpu *vcpu)
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{
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- if (!vcpu->arch.time_page)
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+ if (!vcpu->arch.pv_time_enabled)
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return -EINVAL;
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vcpu->arch.pvclock_set_guest_stopped_request = true;
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kvm_make_request(KVM_REQ_CLOCK_UPDATE, vcpu);
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@@ -6723,6 +6715,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *vcpu)
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goto fail_free_wbinvd_dirty_mask;
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vcpu->arch.ia32_tsc_adjust_msr = 0x0;
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+ vcpu->arch.pv_time_enabled = false;
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kvm_async_pf_hash_reset(vcpu);
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kvm_pmu_init(vcpu);
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