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| author | Andy Honig <ahonig@google.com> | 2013-03-11 09:34:52 -0700 |
|---|---|---|
| committer | Marcelo Tosatti <mtosatti@redhat.com> | 2013-03-19 14:17:31 -0300 |
| commit | c300aa64ddf57d9c5d9c898a64b36877345dd4a9 (patch) | |
| tree | 509c85623ff9e65c383845562db3dbce2da17531 /arch | |
| parent | c09664bb44184b3846e8c5254db4eae4b932682a (diff) | |
| download | lwn-c300aa64ddf57d9c5d9c898a64b36877345dd4a9.tar.gz lwn-c300aa64ddf57d9c5d9c898a64b36877345dd4a9.zip | |
KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796)
If the guest sets the GPA of the time_page so that the request to update the
time straddles a page then KVM will write onto an incorrect page. The
write is done byusing kmap atomic to get a pointer to the page for the time
structure and then performing a memcpy to that page starting at an offset
that the guest controls. Well behaved guests always provide a 32-byte aligned
address, however a malicious guest could use this to corrupt host kernel
memory.
Tested: Tested against kvmclock unit test.
Signed-off-by: Andrew Honig <ahonig@google.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kvm/x86.c | 5 |
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index f7c850b36910..2ade60c25402 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1959,6 +1959,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, struct msr_data *msr_info) /* ...but clean it before doing the actual write */ vcpu->arch.time_offset = data & ~(PAGE_MASK | 1); + /* Check that the address is 32-byte aligned. */ + if (vcpu->arch.time_offset & + (sizeof(struct pvclock_vcpu_time_info) - 1)) + break; + vcpu->arch.time_page = gfn_to_page(vcpu->kvm, data >> PAGE_SHIFT); |