archive_read_format_7zip_bid(struct archive_read *a, int best_bid)
{
	const char *p;

	/* If someone has already bid more than 32, then avoid
	   trashing the look-ahead buffers with a seek. */
	if (best_bid > 32)
		return (-1);

	if ((p = __archive_read_ahead(a, 6, NULL)) == NULL)
		return (0);

	/* If first six bytes are the 7-Zip signature,
	 * return the bid right now. */
	if (memcmp(p, _7ZIP_SIGNATURE, 6) == 0)
		return (48);

	/*
	 * It may a 7-Zip SFX archive file. If first two bytes are
	 * 'M' and 'Z' available on Windows or first four bytes are
	 * "\x7F\x45LF" available on posix like system, seek the 7-Zip
	 * signature. Although we will perform a seek when reading
	 * a header, what we do not use __archive_read_seek() here is
	 * due to a bidding performance.
	 */
	if ((p[0] == 'M' && p[1] == 'Z') || memcmp(p, "\x7F\x45LF", 4) == 0) {
		ssize_t offset = SFX_MIN_ADDR;
		ssize_t window = 4096;
		ssize_t bytes_avail;
		while (offset + window <= (SFX_MAX_ADDR)) {
			const char *buff = __archive_read_ahead(a,
					offset + window, &bytes_avail);
			if (buff == NULL) {
				/* Remaining bytes are less than window. */
				window >>= 1;
				if (window < 0x40)
					return (0);
				continue;
			}
			p = buff + offset;
			while (p + 32 < buff + bytes_avail) {
				int step = check_7zip_header_in_sfx(p);
				if (step == 0)
					return (48);
				p += step;
			}
			offset = p - buff;
		}
	}
	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.