VMCI: Use memdup_user() rather than duplicating its implementation

Reuse existing functionality from memdup_user() instead of keeping
duplicate source code.

This issue was detected by using the Coccinelle software.
Signed-off-by: Wen Yang <wen.yang99@zte.com.cn>
CC: Arnd Bergmann <arnd@arndb.de>
CC: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
CC: linux-kernel@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

drivers/misc/vmw_vmci/vmci_host.c

@@ -750,19 +750,10 @@ static int vmci_host_do_ctx_set_cpt_state(struct vmci_host_dev *vmci_host_dev,
 	if (copy_from_user(&set_info, uptr, sizeof(set_info)))
 		return -EFAULT;
 
-	cpt_buf = kmalloc(set_info.buf_size, GFP_KERNEL);
-	if (!cpt_buf) {
-		vmci_ioctl_err(
-			"cannot allocate memory to set cpt state (type=%d)\n",
-			set_info.cpt_type);
-		return -ENOMEM;
-	}
-
-	if (copy_from_user(cpt_buf, (void __user *)(uintptr_t)set_info.cpt_buf,
-			   set_info.buf_size)) {
-		retval = -EFAULT;
-		goto out;
-	}
+	cpt_buf = memdup_user((void __user *)(uintptr_t)set_info.cpt_buf,
+				set_info.buf_size);
+	if (IS_ERR(cpt_buf))
+		return PTR_ERR(cpt_buf);
 
 	cid = vmci_ctx_get_id(vmci_host_dev->context);
 	set_info.result = vmci_ctx_set_chkpt_state(cid, set_info.cpt_type,
@@ -770,7 +761,6 @@ static int vmci_host_do_ctx_set_cpt_state(struct vmci_host_dev *vmci_host_dev,
 
 	retval = copy_to_user(uptr, &set_info, sizeof(set_info)) ? -EFAULT : 0;
 
-out:
 	kfree(cpt_buf);
 	return retval;
 }