efivarfs: 'efivarfs_file_write' function reorganization

This reorganization removes useless 'bytes' prior assignment and uses
'memdup_user' instead 'kmalloc' + 'copy_from_user'.
Signed-off-by: Geyslan G. Bem <geyslan@gmail.com>
Signed-off-by: Matt Fleming <matt.fleming@intel.com>

fs/efivarfs/file.c

@@ -21,7 +21,7 @@ static ssize_t efivarfs_file_write(struct file *file,
 	u32 attributes;
 	struct inode *inode = file->f_mapping->host;
 	unsigned long datasize = count - sizeof(attributes);
-	ssize_t bytes = 0;
+	ssize_t bytes;
 	bool set = false;
 
 	if (count < sizeof(attributes))
@@ -33,14 +33,9 @@ static ssize_t efivarfs_file_write(struct file *file,
 	if (attributes & ~(EFI_VARIABLE_MASK))
 		return -EINVAL;
 
-	data = kmalloc(datasize, GFP_KERNEL);
-	if (!data)
-		return -ENOMEM;
-
-	if (copy_from_user(data, userbuf + sizeof(attributes), datasize)) {
-		bytes = -EFAULT;
-		goto out;
-	}
+	data = memdup_user(userbuf + sizeof(attributes), datasize);
+	if (IS_ERR(data))
+		return PTR_ERR(data);
 
 	bytes = efivar_entry_set_get_size(var, attributes, &datasize,
 					  data, &set);