From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57296) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZrmZa-00049o-Ot for qemu-devel@nongnu.org; Thu, 29 Oct 2015 08:44:55 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZrmZV-0006MP-LJ for qemu-devel@nongnu.org; Thu, 29 Oct 2015 08:44:54 -0400 Received: from mx1.redhat.com ([209.132.183.28]:35442) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZrmZV-0006Lk-E5 for qemu-devel@nongnu.org; Thu, 29 Oct 2015 08:44:49 -0400 Received: from int-mx13.intmail.prod.int.phx2.redhat.com (int-mx13.intmail.prod.int.phx2.redhat.com [10.5.11.26]) by mx1.redhat.com (Postfix) with ESMTPS id C07F88C1D6 for ; Thu, 29 Oct 2015 12:44:45 +0000 (UTC) From: Markus Armbruster Date: Thu, 29 Oct 2015 13:44:43 +0100 Message-Id: <1446122683-2355-5-git-send-email-armbru@redhat.com> In-Reply-To: <1446122683-2355-1-git-send-email-armbru@redhat.com> References: <1446122683-2355-1-git-send-email-armbru@redhat.com> Subject: [Qemu-devel] [PATCH 4/4] json-streamer: Limit number of tokens in addition to total size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: qemu-devel@nongnu.org Cc: lcapitulino@redhat.com Commit 29c75dd "json-streamer: limit the maximum recursion depth and maximum token count" attempts to guard against excessive heap usage by limiting total token size (it says "token count", but that's a lie). Total token size is a rather imprecise predictor of heap usage: many small tokens use more space than few large tokens with the same input size, because there's a constant per-token overhead. Tighten this up: limit the token count to 128Ki. If you think 128Ki is too stingy: check-qjson's large_dict test eats a sweet 500MiB and pegs a core for four minutes on my machine to parse ~100K tokens. Absurdly wasteful. Signed-off-by: Markus Armbruster --- qobject/json-streamer.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/qobject/json-streamer.c b/qobject/json-streamer.c index 755c74d..df2b4c1 100644 --- a/qobject/json-streamer.c +++ b/qobject/json-streamer.c @@ -19,6 +19,7 @@ #include "qapi/qmp/json-streamer.h" #define MAX_TOKEN_SIZE (64ULL << 20) +#define MAX_TOKEN_COUNT (128ULL << 10) #define MAX_NESTING (1ULL << 10) static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTokenType type, int x, int y) @@ -64,6 +65,7 @@ static void json_message_process_token(JSONLexer *lexer, QString *token, JSONTok parser->bracket_count == 0)) { goto out_emit; } else if (parser->token_size > MAX_TOKEN_SIZE || + qlist_size(parser->tokens) > MAX_TOKEN_COUNT || parser->bracket_count + parser->brace_count > MAX_NESTING) { /* Security consideration, we limit total memory allocated per object * and the maximum recursion depth that a message can force. -- 2.4.3