[cfe-dev] fixing bugs fuzzed out of clang

[Dmitry Polukhin via cfe-dev]

Hi Kostya,

I would like to repro and fix some of the issues that fuzzed found but I
don't have system Clang on my machine but I do have Clang sources so I need
to make Clang to have ASan and after that use that Clang to build Clang one
more time but with ASan enabled. It looks like in Clang doc there is no
info how to do it. I only found LLVM_USE_SANITIZER so I did it like this:

cd $ROOT
mkdir release
cd release
cmake ../llvm -DCMAKE_BUILD_TYPE=Release
make
cd ..
mkdir build
cd build
CC=$ROOT/release/bin/clang CXX=$ROOT/release/bin/clang++ cmake ../llvm
-DCMAKE_BUILD_TYPE=Debug -DLLVM_USE_SANITIZER=Address
make

Last build seems to hang on compilation of llvm/lib/IR/Function.cpp. I
break it after about 30min and 25G RAM consumed. Without -fsanitize=address
compilation takes about 30 sec. Do you have bot that checks self build with
ASan? Is it known issue?

Thanks,
Dmitry
--
Software Engineer
Intel Compiler Team

On Tue, Jan 5, 2016 at 1:46 PM, Andrey Bokhanko via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

> We (Intel clang team) will take a look and fix some of these.
>
> Yours,
> Andrey
> ======
> Software Engineer
> Intel Compiler Team
> Intel
>
>
> On Mon, Jan 4, 2016 at 9:20 PM, Kostya Serebryany via cfe-dev
> <cfe-dev at lists.llvm.org> wrote:
> > Hi Clang devs,
> >
> > In the new year I would like to ask you all to consider fixing clang bugs
> > found by fuzzing (that includes, but is not limited to,
> > https://llvm.org/bugs/show_bug.cgi?id=23057)
> >
> > The existing fuzzer bot is reporting known bugs that are not being fixed
> for
> > months.
> > E.g.
> >
> http://lab.llvm.org:8011/builders/sanitizer-x86_64-linux-fuzzer/builds/5328/steps/stage2%2Fasan%2Bassertions%20run%20clang-fuzzer/logs/stdio
> > This precludes us from treating these bugs as errors and make the bot
> red on
> > regressions.
> >
> > Also, these shallow bugs prevent us from finding deeper bugs with
> potential
> > security implications, and there are some such.
> > E.g. the bug below means that no one can safely host clang as a web
> service.
> >
> > echo "* a ((int () (o W, *&])) 0" | ./bin/clang -x c++ -
> >
> > ==13059==ERROR: AddressSanitizer: heap-use-after-free on address
> > 0x61500000e538 at pc 0x00000081df99 bp 0x7ffdbdcb3630 sp 0x7ffdbdcb2de8
> >
> > READ of size 20 at 0x61500000e538 thread T0
> >     #0 0x81df98 in __asan_memcpy
> >     #1 0xedcd28f in clang::TokenLexer::Lex(clang::Token&)
> > tools/clang/lib/Lex/TokenLexer.cpp:441:7
> >     #2 0xedb3c47 in clang::Preprocessor::Lex(clang::Token&)
> > tools/clang/lib/Lex/Preprocessor.cpp:731:23
> >     #3 0xa5ad93a in ConsumeParen
> > tools/clang/include/clang/Parse/Parser.h:383:5
> >     #4 0xa5ad93a in
> > clang::Parser::SkipUntil(llvm::ArrayRef<clang::tok::TokenKind>,
> > clang::Parser::SkipUntilFlags) tools/clang/lib/Parse/Parser.cpp:3
> >     #5 0xa78bdb8 in SkipUntil
> > tools/clang/include/clang/Parse/Parser.h:864:12
> >
> > 0x61500000e538 is located 312 bytes inside of 456-byte region
> > [0x61500000e400,0x61500000e5c8)
> > freed by thread T0 here:
> >     #0 0x8350db in __interceptor_free
> >     #1 0xa838c02 in ~SmallVectorImpl include/llvm/ADT/SmallVector.h:374:7
> >     #2 0xa838c02 in
> >
> clang::Parser::ParseCXXAmbiguousParenExpression(clang::Parser::ParenParseOption&,
> > clang::OpaquePtr<clang::QualType>&, clang::Bala
> >     #3 0xa7ac905 in
> > clang::Parser::ParseParenExpression(clang::Parser::ParenParseOption&,
> bool,
> > bool, clang::OpaquePtr<clang::QualType>&, clang::Sour
> >     #4 0xa794e83 in clang::Parser::ParseCastExpression(bool, bool, bool&,
> > clang::Parser::TypeCastState) tools/clang/lib/Parse/ParseExpr.cpp:709:11
> >     #5 0xa77c21c in ParseCastExpression
> > tools/clang/lib/Parse/ParseExpr.cpp:465:20
> >
> >
> > --kcc
> >
> > _______________________________________________
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> > cfe-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-dev
> >
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