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Tobias Hieta via llvm-dev

2020-Feb-03 15:53 UTC

[llvm-dev] ASAN not finding any bugs?

Hello,

I am building sanitizers for our different platforms and trying to use
it in an example program, but while it seems like ASAN is running it's
init functions (see stdout below with ASAN_OPTIONS=verbosity=1) it
never catches anything in the program. This is LLVM 8.0.1 btw.

I was using this small test case:

int main(int argc, char** argv) {
  int *array = new int[100];
  delete [] array;
  return array[argc];  // BOOM
}

I am compiling with:


clang++ -resource-dir <path to sanitizers> -fsanitize=address
-shared-libasan -fno-omit-frame-pointer -Os -g -Wl,-rpath,<path to
sanitizers> -o hello hello.cpp

This is the output from setting verbosity=1 - how can I debug this issue?

==3401806==AddressSanitizer: libc interceptors initialized
|| `[0x10007fff8000, 0x7fffffffffff]` || HighMem ||
|| `[0x02008fff7000, 0x10007fff7fff]` || HighShadow ||
|| `[0x00008fff7000, 0x02008fff6fff]` || ShadowGap ||
|| `[0x00007fff8000, 0x00008fff6fff]` || LowShadow ||
|| `[0x000000000000, 0x00007fff7fff]` || LowMem ||
MemToShadow(shadow): 0x00008fff7000 0x000091ff6dff 0x004091ff6e00 0x02008fff6fff
redzone=16
max_redzone=2048
quarantine_size_mb=256M
thread_local_quarantine_size_kb=1024K
malloc_context_size=30
SHADOW_SCALE: 3
SHADOW_GRANULARITY: 8
SHADOW_OFFSET: 0x7fff8000
==3401806==Installed the sigaction for signal 11
==3401806==Installed the sigaction for signal 7
==3401806==Installed the sigaction for signal 8
==3401806==T0: stack [0x7fff3bf5c000,0x7fff3c75c000) size 0x800000;
local=0x7fff3c759244
==3401806==AddressSanitizer Init done

➜ readelf -d hello

Dynamic section at offset 0xe18 contains 25 entries:
Tag Type Name/Value
0x0000000000000001 (NEEDED) Shared library: [libclang_rt.asan-x86_64.so]
0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
0x000000000000000c (INIT) 0x400570
0x000000000000000d (FINI) 0x4007b8
0x0000000000000004 (HASH) 0x400278
0x0000000000000005 (STRTAB) 0x400318
0x0000000000000006 (SYMTAB) 0x4002a0
0x000000000000000a (STRSZ) 462 (bytes)
0x000000000000000b (SYMENT) 24 (bytes)
0x0000000000000015 (DEBUG) 0x0
0x0000000000000003 (PLTGOT) 0x601000
0x0000000000000002 (PLTRELSZ) 72 (bytes)
0x0000000000000014 (PLTREL) RELA
0x0000000000000017 (JMPREL) 0x400528
0x0000000000000007 (RELA) 0x400510
0x0000000000000008 (RELASZ) 24 (bytes)
0x0000000000000009 (RELAENT) 24 (bytes)
0x000000006ffffffe (VERNEED) 0x4004f0
0x000000006fffffff (VERNEEDNUM) 1
0x000000006ffffff0 (VERSYM) 0x4004e6
0x0000000000000000 (NULL) 0x0

Alex Brachet-Mialot via llvm-dev

2020-Feb-03 16:29 UTC

head link

[llvm-dev] ASAN not finding any bugs?

I haven’t looked at the code gen yet because I’m not on my computer right
now but I suspect that at -Os the compiler is optimizing this away because
it knows it to be undefined behavior. Try with -O0.

On Mon, Feb 3, 2020 at 10:53 AM Tobias Hieta via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> Hello,
>
> I am building sanitizers for our different platforms and trying to use
> it in an example program, but while it seems like ASAN is running it's
> init functions (see stdout below with ASAN_OPTIONS=verbosity=1) it
> never catches anything in the program. This is LLVM 8.0.1 btw.
>
> I was using this small test case:
>
> int main(int argc, char** argv) {
>   int *array = new int[100];
>   delete [] array;
>   return array[argc];  // BOOM
> }
>
> I am compiling with:
>
>
> clang++ -resource-dir <path to sanitizers> -fsanitize=address
> -shared-libasan -fno-omit-frame-pointer -Os -g -Wl,-rpath,<path to
> sanitizers> -o hello hello.cpp
>
> This is the output from setting verbosity=1 - how can I debug this issue?
>
> ==3401806==AddressSanitizer: libc interceptors initialized
> || `[0x10007fff8000, 0x7fffffffffff]` || HighMem ||
> || `[0x02008fff7000, 0x10007fff7fff]` || HighShadow ||
> || `[0x00008fff7000, 0x02008fff6fff]` || ShadowGap ||
> || `[0x00007fff8000, 0x00008fff6fff]` || LowShadow ||
> || `[0x000000000000, 0x00007fff7fff]` || LowMem ||
> MemToShadow(shadow): 0x00008fff7000 0x000091ff6dff 0x004091ff6e00
> 0x02008fff6fff
> redzone=16
> max_redzone=2048
> quarantine_size_mb=256M
> thread_local_quarantine_size_kb=1024K
> malloc_context_size=30
> SHADOW_SCALE: 3
> SHADOW_GRANULARITY: 8
> SHADOW_OFFSET: 0x7fff8000
> ==3401806==Installed the sigaction for signal 11
> ==3401806==Installed the sigaction for signal 7
> ==3401806==Installed the sigaction for signal 8
> ==3401806==T0: stack [0x7fff3bf5c000,0x7fff3c75c000) size 0x800000;
> local=0x7fff3c759244
> ==3401806==AddressSanitizer Init done
>
> ➜ readelf -d hello
>
> Dynamic section at offset 0xe18 contains 25 entries:
> Tag Type Name/Value
> 0x0000000000000001 (NEEDED) Shared library: [libclang_rt.asan-x86_64.so]
> 0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
> 0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
> 0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
> 0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
> 0x000000000000000c (INIT) 0x400570
> 0x000000000000000d (FINI) 0x4007b8
> 0x0000000000000004 (HASH) 0x400278
> 0x0000000000000005 (STRTAB) 0x400318
> 0x0000000000000006 (SYMTAB) 0x4002a0
> 0x000000000000000a (STRSZ) 462 (bytes)
> 0x000000000000000b (SYMENT) 24 (bytes)
> 0x0000000000000015 (DEBUG) 0x0
> 0x0000000000000003 (PLTGOT) 0x601000
> 0x0000000000000002 (PLTRELSZ) 72 (bytes)
> 0x0000000000000014 (PLTREL) RELA
> 0x0000000000000017 (JMPREL) 0x400528
> 0x0000000000000007 (RELA) 0x400510
> 0x0000000000000008 (RELASZ) 24 (bytes)
> 0x0000000000000009 (RELAENT) 24 (bytes)
> 0x000000006ffffffe (VERNEED) 0x4004f0
> 0x000000006fffffff (VERNEEDNUM) 1
> 0x000000006ffffff0 (VERSYM) 0x4004e6
> 0x0000000000000000 (NULL) 0x0
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
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Tobias Hieta via llvm-dev

2020-Feb-03 19:38 UTC

head link

[llvm-dev] ASAN not finding any bugs?

Hello Alex,

Thanks for the hint. It was actually not the -O flag that created the
problem. But it pointed me in the right direction, when I passed
-fno-experimental-new-pass-manager it started to show the error. My
guess is that the new pass manager is more aggressive in removing UB?

Thanks,
Tobias

On Mon, Feb 3, 2020 at 5:29 PM Alex Brachet-Mialot
<alexbrachetmialot at gmail.com> wrote:>
> I haven’t looked at the code gen yet because I’m not on my computer right
now but I suspect that at -Os the compiler is optimizing this away because it
knows it to be undefined behavior. Try with -O0.
>
> On Mon, Feb 3, 2020 at 10:53 AM Tobias Hieta via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
>>
>> Hello,
>>
>> I am building sanitizers for our different platforms and trying to use
>> it in an example program, but while it seems like ASAN is running
it's
>> init functions (see stdout below with ASAN_OPTIONS=verbosity=1) it
>> never catches anything in the program. This is LLVM 8.0.1 btw.
>>
>> I was using this small test case:
>>
>> int main(int argc, char** argv) {
>>   int *array = new int[100];
>>   delete [] array;
>>   return array[argc];  // BOOM
>> }
>>
>> I am compiling with:
>>
>>
>> clang++ -resource-dir <path to sanitizers> -fsanitize=address
>> -shared-libasan -fno-omit-frame-pointer -Os -g -Wl,-rpath,<path to
>> sanitizers> -o hello hello.cpp
>>
>> This is the output from setting verbosity=1 - how can I debug this
issue?
>>
>> ==3401806==AddressSanitizer: libc interceptors initialized
>> || `[0x10007fff8000, 0x7fffffffffff]` || HighMem ||
>> || `[0x02008fff7000, 0x10007fff7fff]` || HighShadow ||
>> || `[0x00008fff7000, 0x02008fff6fff]` || ShadowGap ||
>> || `[0x00007fff8000, 0x00008fff6fff]` || LowShadow ||
>> || `[0x000000000000, 0x00007fff7fff]` || LowMem ||
>> MemToShadow(shadow): 0x00008fff7000 0x000091ff6dff 0x004091ff6e00
0x02008fff6fff
>> redzone=16
>> max_redzone=2048
>> quarantine_size_mb=256M
>> thread_local_quarantine_size_kb=1024K
>> malloc_context_size=30
>> SHADOW_SCALE: 3
>> SHADOW_GRANULARITY: 8
>> SHADOW_OFFSET: 0x7fff8000
>> ==3401806==Installed the sigaction for signal 11
>> ==3401806==Installed the sigaction for signal 7
>> ==3401806==Installed the sigaction for signal 8
>> ==3401806==T0: stack [0x7fff3bf5c000,0x7fff3c75c000) size 0x800000;
>> local=0x7fff3c759244
>> ==3401806==AddressSanitizer Init done
>>
>> ➜ readelf -d hello
>>
>> Dynamic section at offset 0xe18 contains 25 entries:
>> Tag Type Name/Value
>> 0x0000000000000001 (NEEDED) Shared library:
[libclang_rt.asan-x86_64.so]
>> 0x0000000000000001 (NEEDED) Shared library: [libstdc++.so.6]
>> 0x0000000000000001 (NEEDED) Shared library: [libm.so.6]
>> 0x0000000000000001 (NEEDED) Shared library: [libgcc_s.so.1]
>> 0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
>> 0x000000000000000c (INIT) 0x400570
>> 0x000000000000000d (FINI) 0x4007b8
>> 0x0000000000000004 (HASH) 0x400278
>> 0x0000000000000005 (STRTAB) 0x400318
>> 0x0000000000000006 (SYMTAB) 0x4002a0
>> 0x000000000000000a (STRSZ) 462 (bytes)
>> 0x000000000000000b (SYMENT) 24 (bytes)
>> 0x0000000000000015 (DEBUG) 0x0
>> 0x0000000000000003 (PLTGOT) 0x601000
>> 0x0000000000000002 (PLTRELSZ) 72 (bytes)
>> 0x0000000000000014 (PLTREL) RELA
>> 0x0000000000000017 (JMPREL) 0x400528
>> 0x0000000000000007 (RELA) 0x400510
>> 0x0000000000000008 (RELASZ) 24 (bytes)
>> 0x0000000000000009 (RELAENT) 24 (bytes)
>> 0x000000006ffffffe (VERNEED) 0x4004f0
>> 0x000000006fffffff (VERNEEDNUM) 1
>> 0x000000006ffffff0 (VERSYM) 0x4004e6
>> 0x0000000000000000 (NULL) 0x0
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev

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