static int __must_check ffs_do_os_descs(unsigned count,
					char *data, unsigned len,
					ffs_os_desc_callback entity, void *priv)
{
	const unsigned _len = len;
	unsigned long num = 0;

	ENTER();

	for (num = 0; num < count; ++num) {
		int ret;
		enum ffs_os_desc_type type;
		u16 feature_count;
		struct usb_os_desc_header *desc = (void *)data;

		if (len < sizeof(*desc))
			return -EINVAL;

		/*
		 * Record "descriptor" entity.
		 * Process dwLength, bcdVersion, wIndex, get b/wCount.
		 * Move the data pointer to the beginning of extended
		 * compatibilities proper or extended properties proper
		 * portions of the data
		 */
		if (le32_to_cpu(desc->dwLength) > len)
			return -EINVAL;

		ret = __ffs_do_os_desc_header(&type, desc);
		if (unlikely(ret < 0)) {
			pr_debug("entity OS_DESCRIPTOR(%02lx); ret = %d\n",
				 num, ret);
			return ret;
		}
		/*
		 * 16-bit hex "?? 00" Little Endian looks like 8-bit hex "??"
		 */
		feature_count = le16_to_cpu(desc->wCount);
		if (type == FFS_OS_DESC_EXT_COMPAT &&
		    (feature_count > 255 || desc->Reserved))
				return -EINVAL;
		len -= ret;
		data += ret;

		/*
		 * Process all function/property descriptors
		 * of this Feature Descriptor
		 */
		ret = ffs_do_single_os_desc(data, len, type,
					    feature_count, entity, priv, desc);
		if (unlikely(ret < 0)) {
			pr_debug("%s returns %d\n", __func__, ret);
			return ret;
		}

		len -= ret;
		data += ret;
	}
	return _len - len;
}

The product reuses or references memory after it has been freed. At some point afterward, the memory may be allocated again and saved in another pointer, while the original pointer references a location somewhere within the new allocation. Any operations using the original pointer are no longer valid because the memory belongs to the code that operates on the new pointer.