521949 - Valgrind warning upon sending "Hello" Message

Status: RESOLVED FIXED

(Core :: IPC, defect)

Description

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

==31546==
==31546== Syscall param socketcall.sendmsg(msg.msg_iov[i]) points to uninitialised byte(s)
==31546==    at 0x4E37FCB: (within /lib64/libpthread-2.9.so)
==31546==    by 0x6ABA007: IPC::Channel::ChannelImpl::ProcessOutgoingMessages() (ipc_channel_posix.cc:598)
==31546==    by 0x6ABA3B3: IPC::Channel::ChannelImpl::Connect() (ipc_channel_posix.cc:350)
==31546==    by 0x6ABA3E4: IPC::Channel::Connect() (ipc_channel_posix.cc:777)
==31546==    by 0x6A19F96: mozilla::ipc::AsyncChannel::OnChannelOpened() (AsyncChannel.cpp:212)
==31546==    by 0x6A1A7F1: void DispatchToMethod<mozilla::ipc::AsyncChannel, void (mozilla::ipc::AsyncChannel::*)()>(mozilla::ipc::AsyncChannel*, void (mozilla::ipc::AsyncChannel::*)(), Tuple0 const&) (tuple.h:383)
==31546==    by 0x6A1A82D: RunnableMethod<mozilla::ipc::AsyncChannel, void (mozilla::ipc::AsyncChannel::*)(), Tuple0>::Run() (task.h:307)
==31546==    by 0x6A4F27E: MessageLoop::RunTask(Task*) (message_loop.cc:322)
==31546==    by 0x6A4F757: MessageLoop::DeferOrRunPendingTask(MessageLoop::PendingTask const&) (message_loop.cc:330)
==31546==    by 0x6A4FADA: MessageLoop::DoWork() (message_loop.cc:430)
==31546==    by 0x6AA8DDC: base::MessagePumpLibevent::Run(base::MessagePump::Delegate*) (message_pump_libevent.cc:224)
==31546==    by 0x6A5001A: MessageLoop::RunInternal() (message_loop.cc:211)
==31546==  Address 0xfc0cdb0 is 24 bytes inside a block of size 64 alloc'd
==31546==    at 0x4C25BC6: malloc (in /usr/lib64/valgrind/amd64-linux/vgpreload_memcheck.so)
==31546==    by 0x4C25DAA: realloc (in /usr/lib64/valgrind/amd64-linux/vgpreload_memcheck.so)
==31546==    by 0x6A5D169: Pickle::Resize(unsigned long) (pickle.cc:419)
==31546==    by 0x6A5D4A4: Pickle::Pickle(int) (pickle.cc:38)
==31546==    by 0x6A93A0F: IPC::Message::Message(int, unsigned short, IPC::Message::PriorityValue) (ipc_message.cc:31)
==31546==    by 0x6ABBFC9: IPC::Channel::ChannelImpl::CreatePipe(std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&, IPC::Channel::Mode) (ipc_channel_posix.cc:315)
==31546==    by 0x6ABC24D: IPC::Channel::ChannelImpl::ChannelImpl(std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&, IPC::Channel::Mode, IPC::Channel::Listener*) (ipc_channel_posix.cc:258)
==31546==    by 0x6ABC390: IPC::Channel::Channel(std::basic_string<wchar_t, std::char_traits<wchar_t>, std::allocator<wchar_t> > const&, IPC::Channel::Mode, IPC::Channel::Listener*) (ipc_channel_posix.cc:769)
==31546==    by 0x6A8A096: ChildThread::Init() (child_thread.cc:106)
==31546==    by 0x6A1CE7A: mozilla::ipc::GeckoThread::Init() (GeckoThread.cpp:61)
==31546==    by 0x6A19AEE: mozilla::plugins::PluginThreadChild::Init() (PluginThreadChild.cpp:67)
==31546==    by 0x6A776D2: base::Thread::ThreadMain() (thread.cc:156)


AFAICT, this happens because the iovec.iov_base in this message header ends up pointing to some IPC::Message::Header fields that are never written to before the Hello() message is sent.  In fact, this same warning should appear when any async or sync message is sent, if my hypothesis is correct.

Not a high priority because although the warning is valid, those fields are never read in the cases where they're never written.

Comment 1

[Chris Jones [:cjones] inactive; ni?/f?/r? if you need me]

Pushed http://hg.mozilla.org/projects/electrolysis/rev/d512dee34413