VMCI: use memdup_user().

Use memdup_user to duplicate a memory region from user-space to
kernel-space, instead of open coding using kmalloc & copy_from_user.
Signed-off-by: Muhammad Falak R Wani <falakreyaz@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/vmw_vmci/vmci_host.c

@@ -381,18 +381,12 @@ static int vmci_host_do_send_datagram(struct vmci_host_dev *vmci_host_dev,
 		return -EINVAL;
 	}
 
-	dg = kmalloc(send_info.len, GFP_KERNEL);
-	if (!dg) {
+	dg = memdup_user((void __user *)(uintptr_t)send_info.addr,
+			 send_info.len);
+	if (IS_ERR(dg)) {
 		vmci_ioctl_err(
 			"cannot allocate memory to dispatch datagram\n");
-		return -ENOMEM;
-	}
-
-	if (copy_from_user(dg, (void __user *)(uintptr_t)send_info.addr,
-			   send_info.len)) {
-		vmci_ioctl_err("error getting datagram\n");
-		kfree(dg);
-		return -EFAULT;
+		return PTR_ERR(dg);
 	}
 
 	if (VMCI_DG_SIZE(dg) != send_info.len) {