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Thu, 12 Nov 2020 07:37:21 +0100 (CET) From: Markus Armbruster To: Alex Chen Subject: Re: [PATCH] json: Fix a memleak in parse_pair() References: <20201111115609.48888-1-alex.chen@huawei.com> Date: Thu, 12 Nov 2020 07:37:21 +0100 In-Reply-To: <20201111115609.48888-1-alex.chen@huawei.com> (Alex Chen's message of "Wed, 11 Nov 2020 11:56:09 +0000") Message-ID: <87imabkrmm.fsf@dusky.pond.sub.org> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.1 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=armbru@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain Received-SPF: pass client-ip=63.128.21.124; envelope-from=armbru@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/11/12 00:52:29 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-trivial@nongnu.org, qemu-devel@nongnu.org, zhang.zhanghailiang@huawei.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Alex Chen writes: > In qobject_type(), NULL is returned when the 'QObject' returned from parse_value() is not of QString type, > and this 'QObject' memory will leaked. > So we need to first check whether the 'QObject' returned from parse_value() is of QString type, > and if not, we free 'QObject' memory and return an error. > > The memleak stack is as follows: > Direct leak of 32 byte(s) in 1 object(s) allocated from: > #0 0xfffe4b3c34fb in __interceptor_malloc (/lib64/libasan.so.4+0xd34fb) > #1 0xfffe4ae48aa3 in g_malloc (/lib64/libglib-2.0.so.0+0x58aa3) > #2 0xaaab3557d9f7 in qnum_from_int /Images/source_org/qemu_master/qemu/qobject/qnum.c:25 > #3 0xaaab35584d23 in parse_literal /Images/source_org/qemu_master/qemu/qobject/json-parser.c:511 > #4 0xaaab35584d23 in parse_value /Images/source_org/qemu_master/qemu/qobject/json-parser.c:554 > #5 0xaaab35583d77 in parse_pair /Images/source_org/qemu_master/qemu/qobject/json-parser.c:270 > #6 0xaaab355845db in parse_object /Images/source_org/qemu_master/qemu/qobject/json-parser.c:327 > #7 0xaaab355845db in parse_value /Images/source_org/qemu_master/qemu/qobject/json-parser.c:546 > #8 0xaaab35585b1b in json_parser_parse /Images/source_org/qemu_master/qemu/qobject/json-parser.c:580 > #9 0xaaab35583703 in json_message_process_token /Images/source_org/qemu_master/qemu/qobject/json-streamer.c:92 > #10 0xaaab355ddccf in json_lexer_feed_char /Images/source_org/qemu_master/qemu/qobject/json-lexer.c:313 > #11 0xaaab355de0eb in json_lexer_feed /Images/source_org/qemu_master/qemu/qobject/json-lexer.c:350 > #12 0xaaab354aff67 in tcp_chr_read /Images/source_org/qemu_master/qemu/chardev/char-socket.c:525 > #13 0xfffe4ae429db in g_main_context_dispatch (/lib64/libglib-2.0.so.0+0x529db) > #14 0xfffe4ae42d8f (/lib64/libglib-2.0.so.0+0x52d8f) > #15 0xfffe4ae430df in g_main_loop_run (/lib64/libglib-2.0.so.0+0x530df) > #16 0xaaab34d70bff in iothread_run /Images/source_org/qemu_master/qemu/iothread.c:82 > #17 0xaaab3559d71b in qemu_thread_start /Images/source_org/qemu_master/qemu/util/qemu-thread-posix.c:519 Good catch, thanks! > Fixes: 532fb5328473 ("qapi: Make more of qobject_to()") > Reported-by: Euler Robot > Signed-off-by: Alex Chen > Signed-off-by: Chen Qun > --- > qobject/json-parser.c | 9 ++++++--- > 1 file changed, 6 insertions(+), 3 deletions(-) > > diff --git a/qobject/json-parser.c b/qobject/json-parser.c > index d083810d37..b37762a203 100644 > --- a/qobject/json-parser.c > +++ b/qobject/json-parser.c > @@ -267,10 +267,13 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict) > goto out; > } > > - key = qobject_to(QString, parse_value(ctxt)); > - if (!key) { > - parse_error(ctxt, peek, "key is not a string in object"); > + value = parse_value(ctxt); > + if (!value || qobject_type(value) != QTYPE_QSTRING) { The "is string" test becomes more cumbersome. Also, we reuse @value for another purpose. > + qobject_unref(value); > + parse_error(ctxt, peek, "value is not a string in object"); Changing error messages in a memory leak fix is inappropriate. Accident? > goto out; > + } else { > + key = qobject_to(QString, value); > } > > token = parser_context_pop_token(ctxt); Here's a simpler, straightforward fix, with a test case thrown in: diff --git a/qobject/json-parser.c b/qobject/json-parser.c index d083810d37..c0f521b56b 100644 --- a/qobject/json-parser.c +++ b/qobject/json-parser.c @@ -257,8 +257,9 @@ static JSONToken *parser_context_peek_token(JSONParserContext *ctxt) */ static int parse_pair(JSONParserContext *ctxt, QDict *dict) { + QObject *key_obj = NULL; + QString *key; QObject *value; - QString *key = NULL; JSONToken *peek, *token; peek = parser_context_peek_token(ctxt); @@ -267,7 +268,8 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict) goto out; } - key = qobject_to(QString, parse_value(ctxt)); + key_obj = parse_value(ctxt); + key = qobject_to(QString, key_obj); if (!key) { parse_error(ctxt, peek, "key is not a string in object"); goto out; @@ -297,13 +299,11 @@ static int parse_pair(JSONParserContext *ctxt, QDict *dict) qdict_put_obj(dict, qstring_get_str(key), value); - qobject_unref(key); - + qobject_unref(key_obj); return 0; out: - qobject_unref(key); - + qobject_unref(key_obj); return -1; } diff --git a/tests/check-qjson.c b/tests/check-qjson.c index 07a773e653..9a02079099 100644 --- a/tests/check-qjson.c +++ b/tests/check-qjson.c @@ -1415,6 +1415,14 @@ static void invalid_dict_comma(void) g_assert(obj == NULL); } +static void invalid_dict_key(void) +{ + Error *err = NULL; + QObject *obj = qobject_from_json("{32:'abc'}", &err); + error_free_or_abort(&err); + g_assert(obj == NULL); +} + static void unterminated_literal(void) { Error *err = NULL; @@ -1500,6 +1508,7 @@ int main(int argc, char **argv) g_test_add_func("/errors/unterminated/dict_comma", unterminated_dict_comma); g_test_add_func("/errors/invalid_array_comma", invalid_array_comma); g_test_add_func("/errors/invalid_dict_comma", invalid_dict_comma); + g_test_add_func("/errors/invalid_dict_key", invalid_dict_key); g_test_add_func("/errors/unterminated/literal", unterminated_literal); g_test_add_func("/errors/limits/nesting", limits_nesting); g_test_add_func("/errors/multiple_values", multiple_values);