Subject: [PATCH 2/6] arm/arm64: KVM: fix potential NULL dereference in user_mem_abort()

From: [email-masked] (Marc Zyngier)
Date: Thu, 09 Oct 2014 14:13:16 +0100

On 09/10/14 14:11, Christoffer Dall wrote:
> On Thu, Oct 09, 2014 at 03:10:08PM +0200, Ard Biesheuvel wrote:
>> On 9 October 2014 15:05, Marc Zyngier <[email-masked]> wrote:
>>> On 17/09/14 22:56, Ard Biesheuvel wrote:
>>>> Handle the potential NULL return value of find_vma_intersection()
>>>> before dereferencing it.
>>>>
>>>> Signed-off-by: Ard Biesheuvel <[email-masked]>
>>>> ---
>>>>  arch/arm/kvm/mmu.c | 6 +++++-
>>>>  1 file changed, 5 insertions(+), 1 deletion(-)
>>>>
>>>> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
>>>> index 152e0f896e63..c093e95ff7ef 100644
>>>> --- a/arch/arm/kvm/mmu.c
>>>> +++ b/arch/arm/kvm/mmu.c
>>>> @@ -776,7 +776,11 @@ static int user_mem_abort(struct kvm_vcpu *vcpu, phys_addr_t fault_ipa,
>>>>       /* Let's check if we will get back a huge page backed by hugetlbfs */
>>>>       down_read(&current->mm->mmap_sem);
>>>>       vma = find_vma_intersection(current->mm, hva, hva + 1);
>>>> -     if (is_vm_hugetlb_page(vma)) {
>>>> +     if (unlikely(!vma)) {
>>>> +             kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
>>>> +             up_read(&current->mm->mmap_sem);
>>>> +             return -EFAULT;
>>>> +     } else if (is_vm_hugetlb_page(vma)) {
>>>
>>> I'm not overly fond of this "else if" construct. The !vma case is final,
>>> so what's after cannot be reached.
>>>
>>
>> I don't have a strong preference either way. I can respin but perhaps
>> Christoffer can fix it up when applying?
>>
> Sure!  Don't respin these just for that.

In which case, please add my

Acked-by: Marc Zyngier <[email-masked]>

when you do the fixup.

Thanks,

	M.
-- 
Jazz is not dead. It just smells funny...