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df649835fe
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: 37 bytes on my
system.
Tighten this up: limit the token count to 2Mi. Chosen to roughly
match the 64MiB total token size limit.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1448486613-17634-13-git-send-email-armbru@redhat.com>
126 lines
3.3 KiB
C
126 lines
3.3 KiB
C
/*
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* JSON streaming support
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*
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* Copyright IBM, Corp. 2009
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*
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* Authors:
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* Anthony Liguori <aliguori@us.ibm.com>
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*
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* This work is licensed under the terms of the GNU LGPL, version 2.1 or later.
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* See the COPYING.LIB file in the top-level directory.
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*
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*/
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#include "qemu-common.h"
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#include "qapi/qmp/json-lexer.h"
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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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{
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if (parser->tokens) {
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g_queue_free(parser->tokens);
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parser->tokens = NULL;
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}
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}
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static void json_message_process_token(JSONLexer *lexer, GString *input,
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JSONTokenType type, int x, int y)
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{
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JSONMessageParser *parser = container_of(lexer, JSONMessageParser, lexer);
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JSONToken *token;
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switch (type) {
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case JSON_LCURLY:
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parser->brace_count++;
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break;
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case JSON_RCURLY:
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parser->brace_count--;
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break;
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case JSON_LSQUARE:
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parser->bracket_count++;
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break;
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case JSON_RSQUARE:
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parser->bracket_count--;
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break;
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default:
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break;
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}
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token = g_malloc(sizeof(JSONToken) + input->len + 1);
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token->type = type;
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memcpy(token->str, input->str, input->len);
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token->str[input->len] = 0;
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token->x = x;
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token->y = y;
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parser->token_size += input->len;
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g_queue_push_tail(parser->tokens, token);
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if (type == JSON_ERROR) {
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goto out_emit_bad;
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} else if (parser->brace_count < 0 ||
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parser->bracket_count < 0 ||
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(parser->brace_count == 0 &&
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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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goto out_emit_bad;
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}
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return;
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out_emit_bad:
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/*
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* Clear out token list and tell the parser to emit an error
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* indication by passing it a NULL list
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*/
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json_message_free_tokens(parser);
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out_emit:
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/* send current list of tokens to parser and reset tokenizer */
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parser->brace_count = 0;
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parser->bracket_count = 0;
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/* parser->emit takes ownership of parser->tokens. */
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parser->emit(parser, parser->tokens);
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parser->tokens = g_queue_new();
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parser->token_size = 0;
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}
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void json_message_parser_init(JSONMessageParser *parser,
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void (*func)(JSONMessageParser *, GQueue *))
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{
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parser->emit = func;
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parser->brace_count = 0;
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parser->bracket_count = 0;
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parser->tokens = g_queue_new();
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parser->token_size = 0;
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json_lexer_init(&parser->lexer, json_message_process_token);
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}
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int json_message_parser_feed(JSONMessageParser *parser,
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const char *buffer, size_t size)
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{
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return json_lexer_feed(&parser->lexer, buffer, size);
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}
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int json_message_parser_flush(JSONMessageParser *parser)
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{
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return json_lexer_flush(&parser->lexer);
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}
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void json_message_parser_destroy(JSONMessageParser *parser)
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{
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json_lexer_destroy(&parser->lexer);
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json_message_free_tokens(parser);
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}
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