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authorDavid Matlack <dmatlack@google.com>2014-08-18 15:46:07 -0700
committerPaolo Bonzini <pbonzini@redhat.com>2014-09-03 10:03:42 +0200
commit56f17dd3fbc44adcdbc3340fe3988ddb833a47a7 (patch)
treea9ca2968a28ef693f00cf1fc01d6590986157e0e
parentee3d1570b58677885b4552bce8217fda7b226a68 (diff)
downloadlinux-56f17dd3fbc44adcdbc3340fe3988ddb833a47a7.tar.bz2
kvm: x86: fix stale mmio cache bug
The following events can lead to an incorrect KVM_EXIT_MMIO bubbling up to userspace: (1) Guest accesses gpa X without a memory slot. The gfn is cached in struct kvm_vcpu_arch (mmio_gfn). On Intel EPT-enabled hosts, KVM sets the SPTE write-execute-noread so that future accesses cause EPT_MISCONFIGs. (2) Host userspace creates a memory slot via KVM_SET_USER_MEMORY_REGION covering the page just accessed. (3) Guest attempts to read or write to gpa X again. On Intel, this generates an EPT_MISCONFIG. The memory slot generation number that was incremented in (2) would normally take care of this but we fast path mmio faults through quickly_check_mmio_pf(), which only checks the per-vcpu mmio cache. Since we hit the cache, KVM passes a KVM_EXIT_MMIO up to userspace. This patch fixes the issue by using the memslot generation number to validate the mmio cache. Cc: stable@vger.kernel.org Signed-off-by: David Matlack <dmatlack@google.com> [xiaoguangrong: adjust the code to make it simpler for stable-tree fix.] Signed-off-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Reviewed-by: David Matlack <dmatlack@google.com> Reviewed-by: Xiao Guangrong <xiaoguangrong@linux.vnet.ibm.com> Tested-by: David Matlack <dmatlack@google.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
-rw-r--r--arch/x86/include/asm/kvm_host.h1
-rw-r--r--arch/x86/kvm/mmu.c2
-rw-r--r--arch/x86/kvm/x86.h20
3 files changed, 17 insertions, 6 deletions
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 73e4149eda33..08cc299ec6f4 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -477,6 +477,7 @@ struct kvm_vcpu_arch {
u64 mmio_gva;
unsigned access;
gfn_t mmio_gfn;
+ u64 mmio_gen;
struct kvm_pmu pmu;
diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c
index 96515957ba82..1cd2a5fbde07 100644
--- a/arch/x86/kvm/mmu.c
+++ b/arch/x86/kvm/mmu.c
@@ -3162,7 +3162,7 @@ static void mmu_sync_roots(struct kvm_vcpu *vcpu)
if (!VALID_PAGE(vcpu->arch.mmu.root_hpa))
return;
- vcpu_clear_mmio_info(vcpu, ~0ul);
+ vcpu_clear_mmio_info(vcpu, MMIO_GVA_ANY);
kvm_mmu_audit(vcpu, AUDIT_PRE_SYNC);
if (vcpu->arch.mmu.root_level == PT64_ROOT_LEVEL) {
hpa_t root = vcpu->arch.mmu.root_hpa;
diff --git a/arch/x86/kvm/x86.h b/arch/x86/kvm/x86.h
index 306a1b77581f..985fb2c006fa 100644
--- a/arch/x86/kvm/x86.h
+++ b/arch/x86/kvm/x86.h
@@ -88,15 +88,23 @@ static inline void vcpu_cache_mmio_info(struct kvm_vcpu *vcpu,
vcpu->arch.mmio_gva = gva & PAGE_MASK;
vcpu->arch.access = access;
vcpu->arch.mmio_gfn = gfn;
+ vcpu->arch.mmio_gen = kvm_memslots(vcpu->kvm)->generation;
+}
+
+static inline bool vcpu_match_mmio_gen(struct kvm_vcpu *vcpu)
+{
+ return vcpu->arch.mmio_gen == kvm_memslots(vcpu->kvm)->generation;
}
/*
- * Clear the mmio cache info for the given gva,
- * specially, if gva is ~0ul, we clear all mmio cache info.
+ * Clear the mmio cache info for the given gva. If gva is MMIO_GVA_ANY, we
+ * clear all mmio cache info.
*/
+#define MMIO_GVA_ANY (~(gva_t)0)
+
static inline void vcpu_clear_mmio_info(struct kvm_vcpu *vcpu, gva_t gva)
{
- if (gva != (~0ul) && vcpu->arch.mmio_gva != (gva & PAGE_MASK))
+ if (gva != MMIO_GVA_ANY && vcpu->arch.mmio_gva != (gva & PAGE_MASK))
return;
vcpu->arch.mmio_gva = 0;
@@ -104,7 +112,8 @@ static inline void vcpu_clear_mmio_info(struct kvm_vcpu *vcpu, gva_t gva)
static inline bool vcpu_match_mmio_gva(struct kvm_vcpu *vcpu, unsigned long gva)
{
- if (vcpu->arch.mmio_gva && vcpu->arch.mmio_gva == (gva & PAGE_MASK))
+ if (vcpu_match_mmio_gen(vcpu) && vcpu->arch.mmio_gva &&
+ vcpu->arch.mmio_gva == (gva & PAGE_MASK))
return true;
return false;
@@ -112,7 +121,8 @@ static inline bool vcpu_match_mmio_gva(struct kvm_vcpu *vcpu, unsigned long gva)
static inline bool vcpu_match_mmio_gpa(struct kvm_vcpu *vcpu, gpa_t gpa)
{
- if (vcpu->arch.mmio_gfn && vcpu->arch.mmio_gfn == gpa >> PAGE_SHIFT)
+ if (vcpu_match_mmio_gen(vcpu) && vcpu->arch.mmio_gfn &&
+ vcpu->arch.mmio_gfn == gpa >> PAGE_SHIFT)
return true;
return false;