read_Folder(struct archive_read *a, struct _7z_folder *f)
{
	struct _7zip *zip = (struct _7zip *)a->format->data;
	const unsigned char *p;
	uint64_t numInStreamsTotal = 0;
	uint64_t numOutStreamsTotal = 0;
	unsigned i;

	memset(f, 0, sizeof(*f));

	/*
	 * Read NumCoders.
	 */
	if (parse_7zip_uint64(a, &(f->numCoders)) < 0)
		return (-1);
	if (f->numCoders > 4)
		/* Too many coders. */
		return (-1);

	f->coders = calloc((size_t)f->numCoders, sizeof(*f->coders));
	if (f->coders == NULL)
		return (-1);
	for (i = 0; i< f->numCoders; i++) {
		size_t codec_size;
		int simple, attr;

		if ((p = header_bytes(a, 1)) == NULL)
			return (-1);
		/*
		 * 0:3 CodecIdSize
		 * 4:  0 - IsSimple
		 *     1 - Is not Simple
		 * 5:  0 - No Attributes
		 *     1 - There are Attributes;
		 * 7:  Must be zero.
		 */
		codec_size = *p & 0xf;
		simple = (*p & 0x10)?0:1;
		attr = *p & 0x20;
		if (*p & 0x80)
			return (-1);/* Not supported. */

		/*
		 * Read Decompression Method IDs.
		 */
		if ((p = header_bytes(a, codec_size)) == NULL)
			return (-1);

		f->coders[i].codec = decode_codec_id(p, codec_size);

		if (simple) {
			f->coders[i].numInStreams = 1;
			f->coders[i].numOutStreams = 1;
		} else {
			if (parse_7zip_uint64(
			    a, &(f->coders[i].numInStreams)) < 0)
				return (-1);
			if (UMAX_ENTRY < f->coders[i].numInStreams)
				return (-1);
			if (parse_7zip_uint64(
			    a, &(f->coders[i].numOutStreams)) < 0)
				return (-1);
			if (UMAX_ENTRY < f->coders[i].numOutStreams)
				return (-1);
		}

		if (attr) {
			if (parse_7zip_uint64(
			    a, &(f->coders[i].propertiesSize)) < 0)
				return (-1);
			if ((p = header_bytes(
			    a, (size_t)f->coders[i].propertiesSize)) == NULL)
				return (-1);
			f->coders[i].properties =
			    malloc((size_t)f->coders[i].propertiesSize);
			if (f->coders[i].properties == NULL)
				return (-1);
			memcpy(f->coders[i].properties, p,
			    (size_t)f->coders[i].propertiesSize);
		}

		numInStreamsTotal += f->coders[i].numInStreams;
		numOutStreamsTotal += f->coders[i].numOutStreams;
	}

	if (numOutStreamsTotal == 0 ||
	    numInStreamsTotal < numOutStreamsTotal-1)
		return (-1);

	f->numBindPairs = numOutStreamsTotal - 1;
	if (zip->header_bytes_remaining < f->numBindPairs)
			return (-1);
	if (f->numBindPairs > 0) {
		f->bindPairs =
			calloc((size_t)f->numBindPairs, sizeof(*f->bindPairs));
		if (f->bindPairs == NULL)
			return (-1);
	} else
		f->bindPairs = NULL;
	for (i = 0; i < f->numBindPairs; i++) {
		if (parse_7zip_uint64(a, &(f->bindPairs[i].inIndex)) < 0)
			return (-1);
		if (UMAX_ENTRY < f->bindPairs[i].inIndex)
			return (-1);
		if (parse_7zip_uint64(a, &(f->bindPairs[i].outIndex)) < 0)
			return (-1);
		if (UMAX_ENTRY < f->bindPairs[i].outIndex)
			return (-1);
	}

	f->numPackedStreams = numInStreamsTotal - f->numBindPairs;
	f->packedStreams =
	    calloc((size_t)f->numPackedStreams, sizeof(*f->packedStreams));
	if (f->packedStreams == NULL)
		return (-1);
	if (f->numPackedStreams == 1) {
		for (i = 0; i < numInStreamsTotal; i++) {
			unsigned j;
			for (j = 0; j < f->numBindPairs; j++) {
				if (f->bindPairs[j].inIndex == i)
					break;
			}
			if (j == f->numBindPairs)
				break;
		}
		if (i == numInStreamsTotal)
			return (-1);
		f->packedStreams[0] = i;
	} else {
		for (i = 0; i < f->numPackedStreams; i++) {
			if (parse_7zip_uint64(a, &(f->packedStreams[i])) < 0)
				return (-1);
			if (UMAX_ENTRY < f->packedStreams[i])
				return (-1);
		}
	}
	f->numInStreams = numInStreamsTotal;
	f->numOutStreams = numOutStreamsTotal;

	return (0);
}

The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.