KVM: Validate userspace_addr of memslot when registered

This way, we can avoid checking the user space address many times when
we read the guest memory.

Although we can do the same for write if we check which slots are
writable, we do not care write now: reading the guest memory happens
more often than writing.

[avi: change VERIFY_READ to VERIFY_WRITE]

Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@oss.ntt.co.jp>
Signed-off-by: Avi Kivity <avi@redhat.com>

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 88ca456..e3f8141 100644 (file)
--- a/arch/x86/kvm/paging_tmpl.h
+++ b/arch/x86/kvm/paging_tmpl.h
@@ -185,7 +185,7 @@ walk:
                }
 
                ptep_user = (pt_element_t __user *)((void *)host_addr + offset);
-               if (unlikely(copy_from_user(&pte, ptep_user, sizeof(pte)))) {
+               if (unlikely(__copy_from_user(&pte, ptep_user, sizeof(pte)))) {
                        present = false;
                        break;
                }

diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index 5814645..ed3c4e7 100644 (file)
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -648,7 +648,10 @@ int __kvm_set_memory_region(struct kvm *kvm,
                goto out;
        if (mem->guest_phys_addr & (PAGE_SIZE - 1))
                goto out;
-       if (user_alloc && (mem->userspace_addr & (PAGE_SIZE - 1)))
+       /* We can read the guest memory with __xxx_user() later on. */
+       if (user_alloc &&
+           ((mem->userspace_addr & (PAGE_SIZE - 1)) ||
+            !access_ok(VERIFY_WRITE, mem->userspace_addr, mem->memory_size)))
                goto out;
        if (mem->slot >= KVM_MEMORY_SLOTS + KVM_PRIVATE_MEM_SLOTS)
                goto out;
@@ -1283,7 +1286,7 @@ int kvm_read_guest_page(struct kvm *kvm, gfn_t gfn, void *data, int offset,
        addr = gfn_to_hva(kvm, gfn);
        if (kvm_is_error_hva(addr))
                return -EFAULT;
-       r = copy_from_user(data, (void __user *)addr + offset, len);
+       r = __copy_from_user(data, (void __user *)addr + offset, len);
        if (r)
                return -EFAULT;
        return 0;