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authorAndy Honig <ahonig@google.com>2013-03-11 09:34:52 -0700
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2013-04-25 21:23:47 -0700
commitd7709255affba50d2ff4087d28308e03d1154afa (patch)
tree0bf8f4a1071a26acbb7bc51ae0200f9596e8e4bb /arch
parent7c72cbc040d7160849369d59166f7be32d1991fd (diff)
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KVM: x86: fix for buffer overflow in handling of MSR_KVM_SYSTEM_TIME (CVE-2013-1796)
commit c300aa64ddf57d9c5d9c898a64b36877345dd4a9 upstream. 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> Cc: Ben Hutchings <ben@decadent.org.uk> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'arch')
-rw-r--r--arch/x86/kvm/x86.c5
1 files changed, 5 insertions, 0 deletions
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c
index e329dc593441..e525b9e3009f 100644
--- a/arch/x86/kvm/x86.c
+++ b/arch/x86/kvm/x86.c
@@ -1539,6 +1539,11 @@ 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);