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From 60ad1bad25ea99c538b745ff95e6e0a877d37d1f Mon Sep 17 00:00:00 2001
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From: Markus Armbruster <armbru@redhat.com>
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Date: Wed, 27 Jul 2016 07:35:11 +0200
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Subject: [PATCH 13/16] qjson: Limit number of tokens in addition to total size
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RH-Author: Markus Armbruster <armbru@redhat.com>
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Message-id: <1469604913-12442-15-git-send-email-armbru@redhat.com>
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Patchwork-id: 71476
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O-Subject: [RHEL-7.3 qemu-kvm PATCH v2 13/15] qjson: Limit number of tokens in addition to total size
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Bugzilla: 1276036
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RH-Acked-by: Miroslav Rezanina <mrezanin@redhat.com>
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RH-Acked-by: John Snow <jsnow@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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Commit 29c75dd "json-streamer: limit the maximum recursion depth and
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maximum token count" attempts to guard against excessive heap usage by
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limiting total token size (it says "token count", but that's a lie).
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Total token size is a rather imprecise predictor of heap usage: many
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small tokens use more space than few large tokens with the same input
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size, because there's a constant per-token overhead: 37 bytes on my
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system.
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Tighten this up: limit the token count to 2Mi. Chosen to roughly
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match the 64MiB total token size limit.
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Signed-off-by: Markus Armbruster <armbru@redhat.com>
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Reviewed-by: Eric Blake <eblake@redhat.com>
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Message-Id: <1448486613-17634-13-git-send-email-armbru@redhat.com>
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(cherry picked from commit df649835fe48f635a93316fdefe96ced7189316e)
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Signed-off-by: Markus Armbruster <armbru@redhat.com>
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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qobject/json-streamer.c | 2 ++
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1 file changed, 2 insertions(+)
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diff --git a/qobject/json-streamer.c b/qobject/json-streamer.c
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index e87230d..a4db4b8 100644
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--- a/qobject/json-streamer.c
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+++ b/qobject/json-streamer.c
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@@ -16,6 +16,7 @@
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#include "qapi/qmp/json-streamer.h"
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#define MAX_TOKEN_SIZE (64ULL << 20)
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+#define MAX_TOKEN_COUNT (2ULL << 20)
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#define MAX_NESTING (1ULL << 10)
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static void json_message_free_tokens(JSONMessageParser *parser)
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@@ -68,6 +69,7 @@ static void json_message_process_token(JSONLexer *lexer, GString *input,
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parser->bracket_count == 0)) {
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goto out_emit;
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} else if (parser->token_size > MAX_TOKEN_SIZE ||
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+ g_queue_get_length(parser->tokens) > MAX_TOKEN_COUNT ||
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parser->bracket_count + parser->brace_count > MAX_NESTING) {
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/* Security consideration, we limit total memory allocated per object
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* and the maximum recursion depth that a message can force.
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--
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1.8.3.1
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