How to unpoison a C++ std::string?

[nolo...@gmail.com]

I'm catching a Msan finding on some STL code. I'm fairly certain I have it narrowed down to the key used in a map, and the key is a string.

I'm fairly sure about the key because of frame 0 and stl_tree.h:1260. Its calling Rb_tree<>::lower_bound using the key. I also unpoisoned the mp and it did not help.

I've tried to instrument the code as follows (from factory.h:114 below), but its not working as expected. Its still catching the finding on the key.

    void RegisterFactory(const std::string &name, ObjectFactory<AbstractClass> *factory)
    {
#ifdef CRYPTOPP_MSAN
        __msan_unpoison(&name, sizeof(std::string));
        __msan_unpoison(&name[0], name.size());
#endif       
        m_map[name] = factory;
    }

How do I unpoison a C++ string?

Or is there a way to say "ignore stuff from the C++ Runtime and associated files"?

==========

$ ./cryptest.exe v 2>&1 | /usr/bin/asan_symbolize
==26988== WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x7f51903b2ca8 in _ZNSt8_Rb_treeISsSt4pairIKSsPvESt10_Select1stIS3_ESt4lessISsESaIS3_EE14_M_lower_boundEPSt13_Rb_tree_nodeIS3_ESC_RS1_ /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/stl_tree.h:1260 (discriminator 1)
    #1 0x7f51903b0fce in _ZNSt3mapISsPvSt4lessISsESaISt4pairIKSsS0_EEEixERS4_ /usr/bin/../lib/gcc/x86_64-linux-gnu/4.9/../../../../include/c++/4.9/bits/stl_map.h:496
    #2 0x7f51903ef9da in _ZN8CryptoPP21ObjectFactoryRegistryINS_18HashTransformationELi0EE15RegisterFactoryERKSsPNS_13ObjectFactoryIS1_EE /home/jwalton/cryptopp/./factory.h:65
    #3 0x7f51903ab51e in RegisterDefaultFactoryFor /home/jwalton/cryptopp/./factory.h:114 (discriminator 6)
    #4 0x7f51903aa93e in _Z17RegisterFactoriesv /home/jwalton/cryptopp/regtest.cpp:70
    #5 0x7f51902ffbf3 in main /home/jwalton/cryptopp/test.cpp:136
    #6 0x7f518e8cab44 in __libc_start_main /build/glibc-h_iKOs/glibc-2.19/csu/libc-start.c:287
    #7 0x7f519027d69c in _start ??:?

SUMMARY: MemorySanitizer: use-of-uninitialized-value ??:0 ??

And:

$ echo " _ZNSt8_Rb_treeISsSt4pairIKSsPvESt10_Select1stIS3_ESt4lessISsESaIS3_EE14_M_lower_boundEPSt13_Rb_tree_nodeIS3_ESC_RS1_" | c++filt

std::_Rb_tree<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, void*>, std::_Select1st<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, void*> >, std::less<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >, std::allocator<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, void*> > >::_M_lower_bound(std::_Rb_tree_node<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, void*> >*, std::_Rb_tree_node<std::pair<std::basic_string<char, std::char_traits<char>, std::allocator<char> > const, void*> >*, std::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)

[Konstantin Serebryany]

please read here: https://github.com/google/sanitizers/wiki/MemorySanitizerLibcxxHowTo

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[nolo...@gmail.com]

On Sunday, February 28, 2016 at 1:08:56 AM UTC-5, Konstantin Serebryany wrote:

please read here: https://github.com/google/sanitizers/wiki/MemorySanitizerLibcxxHowTo

Oh, ouch. But thanks for the help.

Jeff

[Evgenii Stepanov]

Also, use -fsanitize-memory-track-origins, it adds lots of useful info
to the reports.

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