Messages in this thread Patch in this message | | | From | Avi Kivity <> | Subject | [PATCH 34/46] KVM: x86: check for cr3 validity in ioctl_set_sregs | Date | Wed, 20 May 2009 14:18:31 +0300 |
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From: Marcelo Tosatti <mtosatti@redhat.com>
Matt T. Yourst notes that kvm_arch_vcpu_ioctl_set_sregs lacks validity checking for the new cr3 value:
"Userspace callers of KVM_SET_SREGS can pass a bogus value of cr3 to the kernel. This will trigger a NULL pointer access in gfn_to_rmap() when userspace next tries to call KVM_RUN on the affected VCPU and kvm attempts to activate the new non-existent page table root.
This happens since kvm only validates that cr3 points to a valid guest physical memory page when code *inside* the guest sets cr3. However, kvm currently trusts the userspace caller (e.g. QEMU) on the host machine to always supply a valid page table root, rather than properly validating it along with the rest of the reloaded guest state."
http://sourceforge.net/tracker/?func=detail&atid=893831&aid=2687641&group_id=180599
Check for a valid cr3 address in kvm_arch_vcpu_ioctl_set_sregs, triple fault in case of failure.
Cc: stable@kernel.org Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Signed-off-by: Avi Kivity <avi@redhat.com> --- arch/x86/kvm/x86.c | 8 +++++++- 1 files changed, 7 insertions(+), 1 deletions(-)
diff --git a/arch/x86/kvm/x86.c b/arch/x86/kvm/x86.c index a7ea26e..6fc53bb 100644 --- a/arch/x86/kvm/x86.c +++ b/arch/x86/kvm/x86.c @@ -3989,7 +3989,13 @@ int kvm_arch_vcpu_ioctl_set_sregs(struct kvm_vcpu *vcpu, vcpu->arch.cr2 = sregs->cr2; mmu_reset_needed |= vcpu->arch.cr3 != sregs->cr3; - vcpu->arch.cr3 = sregs->cr3; + + down_read(&vcpu->kvm->slots_lock); + if (gfn_to_memslot(vcpu->kvm, sregs->cr3 >> PAGE_SHIFT)) + vcpu->arch.cr3 = sregs->cr3; + else + set_bit(KVM_REQ_TRIPLE_FAULT, &vcpu->requests); + up_read(&vcpu->kvm->slots_lock); kvm_set_cr8(vcpu, sregs->cr8); -- 1.6.0.6
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