Commit message: Fix an error in previous Conditional section patch

an off by one mistake in the change, led to error on correct
document where the end of the included entity was exactly
the end of the conditional section, leading to regtest failure
CVE: CVE-2015-7942
CWE: CWE-119
Vulnerability description: The xmlParseConditionalSections function in parser.c in libxml2 does not properly skip intermediary entities when it stops parsing invalid input, which allows context-dependent attackers to cause a denial of service (out-of-bounds read and crash) via crafted XML data, a different vulnerability than CVE-2015-7941.

Project: libxml2
File: parser.c

xmlParseConditionalSections(xmlParserCtxtPtr ctxt) {
    int id = ctxt->input->id;

    SKIP(3);
    SKIP_BLANKS;
    if (CMP7(CUR_PTR, 'I', 'N', 'C', 'L', 'U', 'D', 'E')) {
	SKIP(7);
	SKIP_BLANKS;
	if (RAW != '[') {
	    xmlFatalErr(ctxt, XML_ERR_CONDSEC_INVALID, NULL);
	    xmlStopParser(ctxt);
	    return;
	} else {
	    if (ctxt->input->id != id) {
		xmlValidityError(ctxt, XML_ERR_ENTITY_BOUNDARY,
	    "All markup of the conditional section is not in the same entity\n",
				     NULL, NULL);
	    }
	    NEXT;
	}
	if (xmlParserDebugEntities) {
	    if ((ctxt->input != NULL) && (ctxt->input->filename))
		xmlGenericError(xmlGenericErrorContext,
			"%s(%d): ", ctxt->input->filename,
			ctxt->input->line);
	    xmlGenericError(xmlGenericErrorContext,
		    "Entering INCLUDE Conditional Section\n");
	}

	while (((RAW != 0) && ((RAW != ']') || (NXT(1) != ']') ||
	        (NXT(2) != '>'))) && (ctxt->instate != XML_PARSER_EOF)) {
	    const xmlChar *check = CUR_PTR;
	    unsigned int cons = ctxt->input->consumed;

	    if ((RAW == '<') && (NXT(1) == '!') && (NXT(2) == '[')) {
		xmlParseConditionalSections(ctxt);
	    } else if (IS_BLANK_CH(CUR)) {
		NEXT;
	    } else if (RAW == '%') {
		xmlParsePEReference(ctxt);
	    } else
		xmlParseMarkupDecl(ctxt);

	    /*
	     * Pop-up of finished entities.
	     */
	    while ((RAW == 0) && (ctxt->inputNr > 1))
		xmlPopInput(ctxt);

	    if ((CUR_PTR == check) && (cons == ctxt->input->consumed)) {
		xmlFatalErr(ctxt, XML_ERR_EXT_SUBSET_NOT_FINISHED, NULL);
		break;
	    }
	}
	if (xmlParserDebugEntities) {
	    if ((ctxt->input != NULL) && (ctxt->input->filename))
		xmlGenericError(xmlGenericErrorContext,
			"%s(%d): ", ctxt->input->filename,
			ctxt->input->line);
	    xmlGenericError(xmlGenericErrorContext,
		    "Leaving INCLUDE Conditional Section\n");
	}

    } else if (CMP6(CUR_PTR, 'I', 'G', 'N', 'O', 'R', 'E')) {
	int state;
	xmlParserInputState instate;
	int depth = 0;

	SKIP(6);
	SKIP_BLANKS;
	if (RAW != '[') {
	    xmlFatalErr(ctxt, XML_ERR_CONDSEC_INVALID, NULL);
	    xmlStopParser(ctxt);
	    return;
	} else {
	    if (ctxt->input->id != id) {
		xmlValidityError(ctxt, XML_ERR_ENTITY_BOUNDARY,
	    "All markup of the conditional section is not in the same entity\n",
				     NULL, NULL);
	    }
	    NEXT;
	}
	if (xmlParserDebugEntities) {
	    if ((ctxt->input != NULL) && (ctxt->input->filename))
		xmlGenericError(xmlGenericErrorContext,
			"%s(%d): ", ctxt->input->filename,
			ctxt->input->line);
	    xmlGenericError(xmlGenericErrorContext,
		    "Entering IGNORE Conditional Section\n");
	}

	/*
	 * Parse up to the end of the conditional section
	 * But disable SAX event generating DTD building in the meantime
	 */
	state = ctxt->disableSAX;
	instate = ctxt->instate;
	if (ctxt->recovery == 0) ctxt->disableSAX = 1;
	ctxt->instate = XML_PARSER_IGNORE;

	while (((depth >= 0) && (RAW != 0)) &&
               (ctxt->instate != XML_PARSER_EOF)) {
	  if ((RAW == '<') && (NXT(1) == '!') && (NXT(2) == '[')) {
	    depth++;
	    SKIP(3);
	    continue;
	  }
	  if ((RAW == ']') && (NXT(1) == ']') && (NXT(2) == '>')) {
	    if (--depth >= 0) SKIP(3);
	    continue;
	  }
	  NEXT;
	  continue;
	}

	ctxt->disableSAX = state;
	ctxt->instate = instate;

	if (xmlParserDebugEntities) {
	    if ((ctxt->input != NULL) && (ctxt->input->filename))
		xmlGenericError(xmlGenericErrorContext,
			"%s(%d): ", ctxt->input->filename,
			ctxt->input->line);
	    xmlGenericError(xmlGenericErrorContext,
		    "Leaving IGNORE Conditional Section\n");
	}

    } else {
	xmlFatalErr(ctxt, XML_ERR_CONDSEC_INVALID_KEYWORD, NULL);
	xmlStopParser(ctxt);
	return;
    }

    if (RAW == 0)
        SHRINK;

    if (RAW == 0) {
	xmlFatalErr(ctxt, XML_ERR_CONDSEC_NOT_FINISHED, NULL);
    } else {
	if (ctxt->input->id != id) {
	    xmlValidityError(ctxt, XML_ERR_ENTITY_BOUNDARY,
	"All markup of the conditional section is not in the same entity\n",
				 NULL, NULL);
	}
	if ((ctxt-> instate != XML_PARSER_EOF) &&
	    ((ctxt->input->cur + 3) < ctxt->input->end))
	    SKIP(3);
    }
}