135 lines
4.0 KiB
Diff
135 lines
4.0 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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[bwh: Backported to 3.2:
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- Adjust context
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- We do not implement the PVCLOCK_GUEST_STOPPED flag]
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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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--- a/arch/x86/include/asm/kvm_host.h
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+++ b/arch/x86/include/asm/kvm_host.h
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@@ -393,8 +393,8 @@ 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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struct {
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u64 msr_val;
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--- a/arch/x86/kvm/x86.c
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+++ b/arch/x86/kvm/x86.c
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@@ -1105,7 +1105,6 @@ static int kvm_guest_time_update(struct
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{
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unsigned long flags;
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struct kvm_vcpu_arch *vcpu = &v->arch;
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- void *shared_kaddr;
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unsigned long this_tsc_khz;
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s64 kernel_ns, max_kernel_ns;
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u64 tsc_timestamp;
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@@ -1141,7 +1140,7 @@ static int kvm_guest_time_update(struct
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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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@@ -1199,14 +1198,9 @@ static int kvm_guest_time_update(struct
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*/
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vcpu->hv_clock.version += 2;
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- shared_kaddr = kmap_atomic(vcpu->time_page, KM_USER0);
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-
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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, KM_USER0);
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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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@@ -1496,10 +1490,7 @@ static int kvm_pv_enable_async_pf(struct
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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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@@ -1591,6 +1582,7 @@ int kvm_set_msr_common(struct kvm_vcpu *
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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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@@ -1600,21 +1592,17 @@ int kvm_set_msr_common(struct kvm_vcpu *
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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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- kvm_release_page_clean(vcpu->arch.time_page);
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- vcpu->arch.time_page = NULL;
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- }
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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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case MSR_KVM_ASYNC_PF_EN:
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@@ -6559,6 +6547,7 @@ int kvm_arch_vcpu_init(struct kvm_vcpu *
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if (!zalloc_cpumask_var(&vcpu->arch.wbinvd_dirty_mask, GFP_KERNEL))
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goto fail_free_mce_banks;
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+ vcpu->arch.pv_time_enabled = false;
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kvm_async_pf_hash_reset(vcpu);
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return 0;
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