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

[Christoffer Dall]

On Thu, Oct 09, 2014 at 03:10:08PM +0200, Ard Biesheuvel wrote:
> On 9 October 2014 15:05, Marc Zyngier <marc.zyngier at arm.com> 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 <ard.biesheuvel at linaro.org>
> >> ---
> >>  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.

-Christoffer