[PATCH 3.14 23/34] arm/arm64: KVM: fix potential NULL dereference in user_mem_abort()

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

3.14-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Ard Biesheuvel <ard.biesheuvel@linaro.org>

commit 37b544087ef3f65ca68465ba39291a07195dac26 upstream.

Handle the potential NULL return value of find_vma_intersection()
before dereferencing it.

Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Shannon Zhao <shannon.zhao@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
 arch/arm/kvm/mmu.c |    6 ++++++
 1 file changed, 6 insertions(+)

--- a/arch/arm/kvm/mmu.c
+++ b/arch/arm/kvm/mmu.c
@@ -778,6 +778,12 @@ static int user_mem_abort(struct kvm_vcp
 	/* 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 (unlikely(!vma)) {
+		kvm_err("Failed to find VMA for hva 0x%lx\n", hva);
+		up_read(&current->mm->mmap_sem);
+		return -EFAULT;
+	}
+
 	if (is_vm_hugetlb_page(vma)) {
 		hugetlb = true;
 		gfn = (fault_ipa & PMD_MASK) >> PAGE_SHIFT;