[cfe-users] MSAN blacklist

[Evgenii Stepanov via cfe-users]

Interceptors are defined here:
  https://github.com/llvm-project/llvm-project-20170507/blob/master/compiler-rt/lib/sanitizer_common/sanitizer_common_interceptors.inc

On Tue, Jan 30, 2018 at 4:17 PM, Bernd Schubert
<bs_lists at aakef.fastmail.fm> wrote:
> Thanks for your help Evgenii!
>
> This is actually another glibc feature and so internal to glibc (in my
> personal opinion, just bloat, but probably not easy to remove nowadays).
>
> This is basically the function
> https://code.woboq.org/userspace/glibc/string/argz-ctsep.c.html
>
> So the argz feature (no idea why this has to be in main glibc)
> https://www.gnu.org/software/libc/manual/html_node/Argz-Functions.html
>
>
> It got a bit late (I shouldn't have tried to compile glibc with llvm), I
> will try to overload/LD_PRELOAD argz_create_sep() tomorrow and memset
> the allocated memory.
> Unfortunately I don't have much control over the user of this function
> this is gnu-libtool / libltdl, which is just copied/linked into the
> project.
>
> I will also open an issue on github, as this is glibc, so these argz
> functions probably should be intersepted by llvm.
> I'm not familiar with llvm code at all. Is it
> llvm::inferLibFuncAttributes(), which defines intercepted functions?
>
>
> Thanks,
> Bernd
>
>
> On 01/29/2018 07:56 PM, Evgenii Stepanov wrote:
>> This is a report from an interceptor, it is not affected by blacklist,
>> unfortunately.
>> You could try MSAN_OPTIONS=intercept_strlen=0, but it is likely that
>> something else will pop up instead.
>> Try figuring out what is the actual reason for the report, i.e. what
>> code is supposed to initialize this memory. Is it some other library
>> that can be built with MSan?
>>
>> A better place for such questions is https://github.com/google/sanitizers/issues
>>
>> On Mon, Jan 29, 2018 at 5:59 AM, Bernd Schubert via cfe-users
>> <cfe-users at lists.llvm.org> wrote:
>>> Hello,
>>>
>>> I would like to blacklist some warnings, but everything I tried
>>> so far is ignored.
>>>
>>> # cat msan-blacklist.txt
>>> fun:*interceptor_strlen*
>>> fun:*foreach_dirinpath*
>>> fun:foreach_dirinpath
>>> fun:*interceptor_strrchr*
>>> fun:*try_dlopen*
>>> src:*/ltdl.c
>>> src:ltdl.c
>>>
>>> So I tried to blacklist all kind of combinations of the failing
>>> functions and also of the related file - without success. It always
>>> fails with the same issue.
>>>
>>>
>>>
>>> Uninitialized bytes in __interceptor_strlen at offset 0 inside
>>> [0x703000035370, 45)
>>> ==3968020==WARNING: MemorySanitizer: use-of-uninitialized-value
>>>     #0 0x7f0f587fa099 in foreach_dirinpath
>>> /home/bschubert/src/cci/gerrit/src/libltdl/ltdl.c:699:18
>>> [...]
>>>
>>>   Uninitialized value was created by a heap allocation
>>>     #0 0x453ebd in __interceptor_malloc (/tmp/ime-server-bernd.0+0x453ebd)
>>>     #1 0x7f0f568c0f7e in __argz_create_sep (/usr/lib64/libc.so.6+0x90f7e)
>>>     #2 0x7f0f585f7775 in _dl_fixup (/lib64/ld-linux-x86-64.so.2+0xe775)
>>>
>>> SUMMARY: MemorySanitizer: use-of-uninitialized-value
>>> /home/bschubert/src/cci/gerrit/src/libltdl/ltdl.c:699:18 in
>>> foreach_dirinpath
>>> Exiting
>>>
>>>
>>> libcci and the main project I'm working on is compiled liked this
>>>
>>> libtool: compile:  /opt/llvm-5.0.1/bin/clang -DHAVE_CONFIG_H -I.
>>> -DLTDLOPEN=libltdlc "-DLT_CONFIG_H=<config.h>" -DLTDL -I. -I. -Ilibltdl
>>> -I./libltdl -I./libltdl -ggdb3 -O2 -fsanitize=memory
>>> -fsanitize-memory-track-origins -fsanitize-memory-use-after-dtor
>>> -fsanitize-blacklist=msan-blacklist.txt -MT libltdlc_la-lt_dlloader.lo
>>> -MD -MP -MF .deps/libltdlc_la-lt_dlloader.Tpo -c lt_dlloader.c  -fPIC
>>> -DPIC -o .libs/libltdlc_la-lt_dlloader.o
>>>
>>>
>>> Any ideas?
>>>
>>>
>>> Thanks,
>>> Bernd
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