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>

2 files changed, 6 insertions, 3 deletions

diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h
index 88ca456ccd68..e3f81418797e 100644
--- 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 58146457bf97..ed3c4e7c1008 100644
--- 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;