Am 25.01.2017 um 10:52 schrieb Paolo Bonzini:
>
>
> ----- Original Message -----
>> From: "David Hildenbrand" <[email protected]>
>> To: "Paolo Bonzini" <[email protected]>, [email protected],
>> [email protected]
>> Cc: [email protected]
>> Sent: Wednesday, January 25, 2017 10:31:13 AM
>> Subject: Re: [PATCH] kvm: fix page struct leak in handle_vmon
>>
>> Am 24.01.2017 um 11:56 schrieb Paolo Bonzini:
>>> handle_vmon gets a reference on VMXON region page,
>>> but does not release it. Release the reference.
>>>
>>> Found by syzkaller; based on a patch by Dmitry.
>>>
>>> Reported-by: Dmitry Vyukov <[email protected]>
>>> Signed-off-by: Paolo Bonzini <[email protected]>
>>> ---
>>> arch/x86/kvm/vmx.c | 9 +++++++--
>>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>>
>>> diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
>>> index 42cc3d6f4d20..0f7345035210 100644
>>> --- a/arch/x86/kvm/vmx.c
>>> +++ b/arch/x86/kvm/vmx.c
>>> @@ -7085,13 +7085,18 @@ static int nested_vmx_check_vmptr(struct kvm_vcpu
>>> *vcpu, int exit_reason,
>>> }
>>>
>>> page = nested_get_page(vcpu, vmptr);
>>> - if (page == NULL ||
>>> - *(u32 *)kmap(page) != VMCS12_REVISION) {
>>> + if (page == NULL) {
>>> nested_vmx_failInvalid(vcpu);
>>> + return kvm_skip_emulated_instruction(vcpu);
>>> + }
>>> + if (*(u32 *)kmap(page) != VMCS12_REVISION) {
>>
>> shouldn't we also check if kmap even returned a valid pointer before
>> dereferencing it?
>
> I don't think kmap can fail (page_address can)?
Then I wonder why there are some checks:
e.g. nested_vmx_merge_msr_bitmap()
msr_bitmap_l1 = (unsigned long *)kmap(page);
if (!msr_bitmap_l1) {
// no unmap
...
return false;
or vmx_complete_nested_posted_interrupt()
vapic_page = kmap(vmx->nested.virtual_apic_page);
if (!vapic_page) {
// no unmap
...
return -ENOMEM;
But there is also no check in handle_vmptrld() for example.
>
> Paolo
--
David
