unpack_bz2_stream(transformer_state_t *xstate)
{
	IF_DESKTOP(long long total_written = 0;)
	bunzip_data *bd;
	char *outbuf;
	int i;
	unsigned len;

	if (check_signature16(xstate, BZIP2_MAGIC))
		return -1;

	outbuf = xmalloc(IOBUF_SIZE);
	len = 0;
	while (1) { /* "Process one BZ... stream" loop */

		i = start_bunzip(&bd, xstate->src_fd, outbuf + 2, len);

		if (i == 0) {
			while (1) { /* "Produce some output bytes" loop */
				i = read_bunzip(bd, outbuf, IOBUF_SIZE);
				if (i < 0) /* error? */
					break;
				i = IOBUF_SIZE - i; /* number of bytes produced */
				if (i == 0) /* EOF? */
					break;
				if (i != transformer_write(xstate, outbuf, i)) {
					i = RETVAL_SHORT_WRITE;
					goto release_mem;
				}
				IF_DESKTOP(total_written += i;)
			}
		}

		if (i != RETVAL_LAST_BLOCK
		/* Observed case when i == RETVAL_OK:
		 * "bzcat z.bz2", where "z.bz2" is a bzipped zero-length file
		 * (to be exact, z.bz2 is exactly these 14 bytes:
		 * 42 5a 68 39 17 72 45 38  50 90 00 00 00 00).
		 */
		 && i != RETVAL_OK
		) {
			bb_error_msg("bunzip error %d", i);
			break;
		}
		if (bd->headerCRC != bd->totalCRC) {
			bb_error_msg("CRC error");
			break;
		}

		/* Successfully unpacked one BZ stream */
		i = RETVAL_OK;

		/* Do we have "BZ..." after last processed byte?
		 * pbzip2 (parallelized bzip2) produces such files.
		 */
		len = bd->inbufCount - bd->inbufPos;
		memcpy(outbuf, &bd->inbuf[bd->inbufPos], len);
		if (len < 2) {
			if (safe_read(xstate->src_fd, outbuf + len, 2 - len) != 2 - len)
				break;
			len = 2;
		}
		if (*(uint16_t*)outbuf != BZIP2_MAGIC) /* "BZ"? */
			break;
		dealloc_bunzip(bd);
		len -= 2;
	}

 release_mem:
	dealloc_bunzip(bd);
	free(outbuf);

	return i ? i : IF_DESKTOP(total_written) + 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.