From patchwork Fri Mar 11 21:00:47 2011 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Anthony Liguori X-Patchwork-Id: 86454 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [199.232.76.165]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id DCDB5B6F12 for ; Sat, 12 Mar 2011 08:12:46 +1100 (EST) Received: from localhost ([127.0.0.1]:34514 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Py9da-0002p7-H8 for incoming@patchwork.ozlabs.org; Fri, 11 Mar 2011 16:12:42 -0500 Received: from [140.186.70.92] (port=47054 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Py9Se-0005xv-TR for qemu-devel@nongnu.org; Fri, 11 Mar 2011 16:01:25 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Py9Sd-0008OX-Sq for qemu-devel@nongnu.org; Fri, 11 Mar 2011 16:01:24 -0500 Received: from e34.co.us.ibm.com ([32.97.110.152]:50248) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Py9Sd-0008MC-Nd for qemu-devel@nongnu.org; Fri, 11 Mar 2011 16:01:23 -0500 Received: from d03relay02.boulder.ibm.com (d03relay02.boulder.ibm.com [9.17.195.227]) by e34.co.us.ibm.com (8.14.4/8.13.1) with ESMTP id p2BKnUCC026226 for ; Fri, 11 Mar 2011 13:49:30 -0700 Received: from d03av04.boulder.ibm.com (d03av04.boulder.ibm.com [9.17.195.170]) by d03relay02.boulder.ibm.com (8.13.8/8.13.8/NCO v9.1) with ESMTP id p2BL1CcX104590 for ; Fri, 11 Mar 2011 14:01:12 -0700 Received: from d03av04.boulder.ibm.com (loopback [127.0.0.1]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id p2BL1COJ009533 for ; Fri, 11 Mar 2011 14:01:12 -0700 Received: from localhost.localdomain (sig-9-65-217-31.mts.ibm.com [9.65.217.31]) by d03av04.boulder.ibm.com (8.14.4/8.13.1/NCO v10.0 AVin) with ESMTP id p2BL0u8q008003; Fri, 11 Mar 2011 14:01:11 -0700 From: Anthony Liguori To: qemu-devel@nongnu.org Date: Fri, 11 Mar 2011 15:00:47 -0600 Message-Id: <1299877249-13433-10-git-send-email-aliguori@us.ibm.com> X-Mailer: git-send-email 1.7.0.4 In-Reply-To: <1299877249-13433-1-git-send-email-aliguori@us.ibm.com> References: <1299877249-13433-1-git-send-email-aliguori@us.ibm.com> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) X-Received-From: 32.97.110.152 Cc: Paolo Bonzini , Anthony Liguori , Markus Armbruster , Michael D Roth , Luiz Capitulino Subject: [Qemu-devel] [PATCH 09/11] json-lexer: limit the maximum size of a given token X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org Errors-To: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org This is a security consideration. We don't want a client to cause an arbitrary amount of memory to be allocated in QEMU. For now, we use a limit of 64MB which should be large enough for any reasonably sized token. This is important for parsing JSON from untrusted sources. Signed-off-by: Anthony Liguori diff --git a/json-lexer.c b/json-lexer.c index 834d7af..3462c89 100644 --- a/json-lexer.c +++ b/json-lexer.c @@ -18,6 +18,8 @@ #include "qemu-common.h" #include "json-lexer.h" +#define MAX_TOKEN_SIZE (64ULL << 20) + /* * \"([^\\\"]|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*\" * '([^\\']|(\\\"\\'\\\\\\/\\b\\f\\n\\r\\t\\u[0-9a-fA-F][0-9a-fA-F][0-9a-fA-F][0-9a-fA-F]))*' @@ -312,6 +314,17 @@ static int json_lexer_feed_char(JSONLexer *lexer, char ch) } lexer->state = new_state; } while (!char_consumed); + + /* Do not let a single token grow to an arbitrarily large size, + * this is a security consideration. + */ + if (lexer->token->length > MAX_TOKEN_SIZE) { + lexer->emit(lexer, lexer->token, lexer->state, lexer->x, lexer->y); + QDECREF(lexer->token); + lexer->token = qstring_new(); + lexer->state = IN_START; + } + return 0; }