| Message ID | 1365161596-11996-1-git-send-email-luis.henriques@canonical.com |
|---|---|
| State | New |
| Headers | show |
On 05.04.2013 13:33, Luis Henriques wrote: > From: Andy Honig <ahonig@google.com> > > CVE-2013-1796 > > BugLink: http://bugs.launchpad.net/bugs/1158254 > > 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> > (cherry picked from commit c300aa64ddf57d9c5d9c898a64b36877345dd4a9) > > Signed-off-by: Luis Henriques <luis.henriques@canonical.com> > --- > arch/x86/kvm/x86.c | 5 +++++ > 1 file changed, 5 insertions(+) > > diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c > index a52bd56..3fee182 100644 > --- a/arch/x86/kvm/x86.c > +++ b/arch/x86/kvm/x86.c > @@ -1635,6 +1635,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) > /* ...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); > > Its cherry-picked. Still don't like the implicit assumptions. :-P But ack anyway.
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a52bd56..3fee182 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -1635,6 +1635,11 @@ int kvm_set_msr_common(struct kvm_vcpu *vcpu, u32 msr, u64 data) /* ...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);