Re: [PATCH 1/2] ARM: KVM: fix NULL pointer dereference when VMA not found

[Christoffer Dall <christoffer.dall@xxxxxxxxxx>]

On Tue, Mar 18, 2014 at 09:45:14PM +0100, Antonios Motakis wrote:
> If the user tries to access an invalid memory region, a NULL pointer
> dereference may happen inside the kernel. Handle this more gracefully.
> 
> Signed-off-by: Nikolay Nikolaev <n.nikolaev@xxxxxxxxxxxxxxxxxxxxxx>
> Signed-off-by: Antonios Motakis <a.motakis@xxxxxxxxxxxxxxxxxxxxxx>
> ---
>  arch/arm/kvm/mmu.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/arch/arm/kvm/mmu.c b/arch/arm/kvm/mmu.c
> index 7789857..7466e56 100644
> --- a/arch/arm/kvm/mmu.c
> +++ b/arch/arm/kvm/mmu.c
> @@ -662,7 +662,7 @@ 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 (likely(vma) && is_vm_hugetlb_page(vma)) {
>  		hugetlb = true;
>  		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;
>  	} else {
> -- 
> 1.8.3.2
> 

Could we use kvm_host_page_size() for this entire thing instead?

-Christoffer
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