KVM: x86: Convert MSR_KVM_SYSTEM_TIME to use gfn_to_hva_cache functions (CVE-2013-1797)
There is a potential use after free issue with the handling of
MSR_KVM_SYSTEM_TIME. If the guest specifies a GPA in a movable or removable
memory such as frame buffers then KVM might continue to write to that
address even after it's removed via KVM_SET_USER_MEMORY_REGION. KVM pins
the page in memory so it's unlikely to cause an issue, but if the user
space component re-purposes the memory previously used for the guest, then
the guest will be able to corrupt that memory.
Tested: Tested against kvmclock unit test
Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
diff --git a/arch/x86/include/asm/kvm_host.h b/arch/x86/include/asm/kvm_host.h
index 635a74d..4979778 100644
--- a/arch/x86/include/asm/kvm_host.h
+++ b/arch/x86/include/asm/kvm_host.h
@@ -414,8 +414,8 @@
gpa_t time;
struct pvclock_vcpu_time_info hv_clock;
unsigned int hw_tsc_khz;
- unsigned int time_offset;
- struct page *time_page;
+ struct gfn_to_hva_cache pv_time;
+ bool pv_time_enabled;
/* set guest stopped flag in pvclock flags field */
bool pvclock_set_guest_stopped_request;