static ssize_t f2fs_quota_write(struct super_block *sb, int type,
				const char *data, size_t len, loff_t off)
{
	struct inode *inode = sb_dqopt(sb)->files[type];
	struct address_space *mapping = inode->i_mapping;
	const struct address_space_operations *a_ops = mapping->a_ops;
	int offset = off & (sb->s_blocksize - 1);
	size_t towrite = len;
	struct page *page;
	char *kaddr;
	int err = 0;
	int tocopy;

	while (towrite > 0) {
		tocopy = min_t(unsigned long, sb->s_blocksize - offset,
								towrite);

		err = a_ops->write_begin(NULL, mapping, off, tocopy, 0,
							&page, NULL);
		if (unlikely(err))
			break;

		kaddr = kmap_atomic(page);
		memcpy(kaddr + offset, data, tocopy);
		kunmap_atomic(kaddr);
		flush_dcache_page(page);

		a_ops->write_end(NULL, mapping, off, tocopy, tocopy,
						page, NULL);
		offset = 0;
		towrite -= tocopy;
		off += tocopy;
		data += tocopy;
		cond_resched();
	}

	if (len == towrite)
		return 0;
	inode->i_version++;
	inode->i_mtime = inode->i_ctime = current_time(inode);
	f2fs_mark_inode_dirty_sync(inode, false);
	return len - towrite;
}

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.