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MarcoFalke ecca2ea1d5
Merge #18785: Prevent valgrind false positive in rest_blockhash_by_height 
fcb7261625 Prevent valgrind false positive in rest_blockhash_by_height (Russell Yanofsky)

Pull request description:

  A bad interaction between valgrind and clang 6.0.0-1ubuntu2 with -O2 optimizations makes valgrind misleadingly imply C++ code is reading an uninitialized blockheight value in `rest_blockhash_by_height` just because that's what clang optimized code is doing. The C++ code looks like:

  ```c++
  int32_t blockheight;
  if (!ParseInt32(height_str, &blockheight) || blockheight < 0) {
  ```

  while the optimized code looks like:

  ```
  0x00000000000f97ab <+123>:   callq  0x4f8860 <ParseInt32(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&, int*)>
  0x00000000000f97b0 <+128>:   mov    0xc(%rsp),%ebx
  0x00000000000f97b4 <+132>:   test   %ebx,%ebx
  0x00000000000f97b6 <+134>:   js     0xf98aa <rest_blockhash_by_height(util::Ref const&, HTTPRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)+378>
  0x00000000000f97bc <+140>:   xor    $0x1,%al
  0x00000000000f97be <+142>:   jne    0xf98aa <rest_blockhash_by_height(util::Ref const&, HTTPRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&)+378>
  ```

  During the rest_interface.py test:

  eef90c14ed/test/functional/interface_rest.py (L266)

  when `height_str` is empty, `ParseInt32` returns false and `blockheight` value is never assigned. The optimized code reads the uninitialized `blockheight` value in `0xc(%rsp)` before the checking the `ParseInt32` return value in `%al`, which is harmless, but triggers the following error from valgrind:

  ```
  ==30660== Thread 13 b-httpworker.2:
  ==30660== Conditional jump or move depends on uninitialised value(s)
  ==30660==    at 0x2017B6: rest_blockhash_by_height(util::Ref const&, HTTPRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (rest.cpp:614)
  ==30660==    by 0x2041B9: operator() (rest.cpp:670)
  ==30660==    by 0x2041B9: std::_Function_handler<bool (HTTPRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&), StartREST(util::Ref const&)::$_1>::_M_invoke(std::_Any_data const&, HTTPRequest*&&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (std_function.h:301)
  ==30660==    by 0x3EC994: operator() (std_function.h:706)
  ==30660==    by 0x3EC994: HTTPWorkItem::operator()() (httpserver.cpp:55)
  ==30660==    by 0x3ED16D: WorkQueue<HTTPClosure>::Run() (httpserver.cpp:114)
  ==30660==    by 0x3E9168: HTTPWorkQueueRun(WorkQueue<HTTPClosure>*, int) (httpserver.cpp:342)
  ==30660==    by 0x3EDAAA: __invoke_impl<void, void (*)(WorkQueue<HTTPClosure> *, int), WorkQueue<HTTPClosure> *, int> (invoke.h:60)
  ==30660==    by 0x3EDAAA: __invoke<void (*)(WorkQueue<HTTPClosure> *, int), WorkQueue<HTTPClosure> *, int> (invoke.h:95)
  ==30660==    by 0x3EDAAA: _M_invoke<0, 1, 2> (thread:234)
  ==30660==    by 0x3EDAAA: operator() (thread:243)
  ==30660==    by 0x3EDAAA: std:🧵:_State_impl<std:🧵:_Invoker<std::tuple<void (*)(WorkQueue<HTTPClosure>*, int), WorkQueue<HTTPClosure>*, int> > >::_M_run() (thread:186)
  ==30660==    by 0x64256DE: ??? (in /usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25)
  ==30660==    by 0x54876DA: start_thread (pthread_create.c:463)
  ==30660==    by 0x6DC888E: clone (clone.S:95)
  ==30660==  Uninitialised value was created by a stack allocation
  ==30660==    at 0x20173A: rest_blockhash_by_height(util::Ref const&, HTTPRequest*, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> > const&) (rest.cpp:608)
  ==30660==
  {
     <insert_a_suppression_name_here>
     Memcheck:Cond
     fun:_ZL24rest_blockhash_by_heightRKN4util3RefEP11HTTPRequestRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEE
     fun:operator()
     fun:_ZNSt17_Function_handlerIFbP11HTTPRequestRKNSt7__cxx1112basic_stringIcSt11char_traitsIcESaIcEEEEZ9StartRESTRKN4util3RefEE3$_1E9_M_invokeERKSt9_Any_dataOS1_S9_
     fun:operator()
     fun:_ZN12HTTPWorkItemclEv
     fun:_ZN9WorkQueueI11HTTPClosureE3RunEv
     fun:_ZL16HTTPWorkQueueRunP9WorkQueueI11HTTPClosureEi
     fun:__invoke_impl<void, void (*)(WorkQueue<HTTPClosure> *, int), WorkQueue<HTTPClosure> *, int>
     fun:__invoke<void (*)(WorkQueue<HTTPClosure> *, int), WorkQueue<HTTPClosure> *, int>
     fun:_M_invoke<0, 1, 2>
     fun:operator()
     fun:_ZNSt6thread11_State_implINS_8_InvokerISt5tupleIJPFvP9WorkQueueI11HTTPClosureEiES6_iEEEEE6_M_runEv
     obj:/usr/lib/x86_64-linux-gnu/libstdc++.so.6.0.25
     fun:start_thread
     fun:clone
  }
  ```

  This is a known bad interaction between clang and valgrind. The clang optimized code is correct but valgrind has no way of knowing that accessing the uninitialized value isn't a problem. Issue has been reported previously:

  - https://bugs.llvm.org/show_bug.cgi?id=32604#c4
  - https://github.com/Z3Prover/z3/issues/972

  This commit just sets blockheight to -1 as a workaround.

  This change was originally made in 41d5d651594c6c939add7a58b7e30c97dccdf24a from #18740 to fix the travis error there (https://travis-ci.org/github/bitcoin/bitcoin/jobs/678453061#L7157) but MarcoFalke suggested https://github.com/bitcoin/bitcoin/pull/18740#discussion_r414772851 moving to a new PR, since apparently the error's been seen on travis previously

ACKs for top commit:
  MarcoFalke:
    ACK fcb7261625
  practicalswift:
    ACK fcb7261625

Tree-SHA512: ec8abf45bd3d6c6e0e7e404d0b2a749efd43910619b84b0b5fe7dab22881598d1011a0f3ff2e146bf46320b63eb152bf63c62c06f1ab84c35dd640abc468f18f
2020-04-29 08:23:06 -04:00
.github Remove GitHub Actions CI workflow. 2020-01-30 18:45:28 +00:00
.tx tx: Bump transifex slug to 020x 2020-03-16 10:52:55 +01:00
build-aux/m4 build: Update ax_boost_mase.m4 to the latest serial 2020-04-08 16:14:31 +03:00
build_msvc scripted-diff: Bump copyright headers 2020-04-16 13:33:09 -04:00
ci Merge #18735: ci: Add and document BASE_BUILD_DIR 2020-04-28 11:50:21 -04:00
contrib Merge #18556: build: Drop make dist in gitian builds 2020-04-28 16:44:17 +08:00
depends Revert "Merge #16367: Multiprocess build support" 2020-04-10 19:38:21 -04:00
doc Merge #18739: doc: Document how to fuzz Bitcoin Core using Honggfuzz 2020-04-25 09:26:52 -04:00
share Merge #18556: build: Drop make dist in gitian builds 2020-04-28 16:44:17 +08:00
src Merge #18785: Prevent valgrind false positive in rest_blockhash_by_height 2020-04-29 08:23:06 -04:00
test Merge #18038: P2P: Mempool tracks locally submitted transactions to improve wallet privacy 2020-04-29 16:32:37 +08:00
.appveyor.yml Merge #18640: appveyor: Remove clcache 2020-04-15 16:19:52 -04:00
.cirrus.yml appveyor: Disable functional tests for now 2020-04-14 09:15:18 -04:00
.gitattributes Separate protocol versioning from clientversion 2014-10-29 00:24:40 -04:00
.gitignore Revert "Merge #16367: Multiprocess build support" 2020-04-10 19:38:21 -04:00
.python-version .python-version: Specify full version 3.5.6 2019-03-02 12:06:26 -05:00
.style.yapf test: .style.yapf: Set column_limit=160 2019-03-04 18:28:13 -05:00
.travis.yml Revert "Merge #16367: Multiprocess build support" 2020-04-10 19:38:21 -04:00
autogen.sh scripted-diff: Bump copyright of files changed in 2019 2019-12-30 10:42:20 +13:00
configure.ac doc: Better explain GNU ld's dislike of ld64's options 2020-04-27 11:08:51 +08:00
CONTRIBUTING.md Merge #18283: doc: Explain rebase policy in CONTRIBUTING.md 2020-03-11 16:01:25 +01:00
COPYING doc: Update license year range to 2020 2019-12-26 23:11:21 +01:00
INSTALL.md Update INSTALL landing redirection notice for build instructions. 2016-10-06 12:27:23 +13:00
libbitcoinconsensus.pc.in build: remove libcrypto as internal dependency in libbitcoinconsensus.pc 2019-11-19 15:03:44 +01:00
Makefile.am Merge #18107: build: Add cov_fuzz target 2020-03-27 14:29:48 +01:00
README.md Adding build instructions to Bitcoin Core, fixes #18658 2020-04-16 21:01:00 -07:00
SECURITY.md doc: Remove explicit mention of version from SECURITY.md 2019-06-14 06:39:17 -04:00

README.md

Bitcoin Core integration/staging tree

https://bitcoincore.org

What is Bitcoin?

Bitcoin is an experimental digital currency that enables instant payments to anyone, anywhere in the world. Bitcoin uses peer-to-peer technology to operate with no central authority: managing transactions and issuing money are carried out collectively by the network. Bitcoin Core is the name of open source software which enables the use of this currency.

For more information, as well as an immediately usable, binary version of the Bitcoin Core software, see https://bitcoincore.org/en/download/, or read the original whitepaper.

License

Bitcoin Core is released under the terms of the MIT license. See COPYING for more information or see https://opensource.org/licenses/MIT.

Development Process

The master branch is regularly built (see doc/build-*.md for instructions) and tested, but is not guaranteed to be completely stable. Tags are created regularly to indicate new official, stable release versions of Bitcoin Core.

The contribution workflow is described in CONTRIBUTING.md and useful hints for developers can be found in doc/developer-notes.md.

Testing

Testing and code review is the bottleneck for development; we get more pull requests than we can review and test on short notice. Please be patient and help out by testing other people's pull requests, and remember this is a security-critical project where any mistake might cost people lots of money.

Automated Testing

Developers are strongly encouraged to write unit tests for new code, and to submit new unit tests for old code. Unit tests can be compiled and run (assuming they weren't disabled in configure) with: make check. Further details on running and extending unit tests can be found in /src/test/README.md.

There are also regression and integration tests, written in Python, that are run automatically on the build server. These tests can be run (if the test dependencies are installed) with: test/functional/test_runner.py

The Travis CI system makes sure that every pull request is built for Windows, Linux, and macOS, and that unit/sanity tests are run automatically.

Manual Quality Assurance (QA) Testing

Changes should be tested by somebody other than the developer who wrote the code. This is especially important for large or high-risk changes. It is useful to add a test plan to the pull request description if testing the changes is not straightforward.

Translations

Changes to translations as well as new translations can be submitted to Bitcoin Core's Transifex page.

Translations are periodically pulled from Transifex and merged into the git repository. See the translation process for details on how this works.

Important: We do not accept translation changes as GitHub pull requests because the next pull from Transifex would automatically overwrite them again.

Translators should also subscribe to the mailing list.