ASAN detected memory leaks at strange position.

[yangluoshen]

Hello everybody，I'm new for ASAN and I get some trouble while using ASAN. Could anybody give me a hand? Thanks a lot!!!

My machine infomation:

# uname -a
Linux SZX1000064851 3.0.76-0.11-default #1 SMP Fri Jun 14 08:21:43 UTC 2013 (ccab990) x86_64 x86_64 x86_64 GNU/Linu
# cat /proc/version
Linux version 3.0.76-0.11-default (geeko@buildhost) (gcc version 4.3.4 [gcc-4_3-branch revision 152973] (SUSE Linux) ) #1 SMP Fri Jun 14 08:21:43 UTC 2013 (ccab990)

and I installed gcc-6.2.0 on /opt/gcc-6.2.0/
I set the LD_LIBRARY_PATH and LD_PRELOAD like following:

# echo $LD_LIBRARY_PATH
:/opt/gmp-6.1.1/lib/:/opt/mpfr-3.1.5/lib/:/opt/mpc-1.0.3/lib/:/opt/gcc-6.2.0/lib64/:/opt/gcc-6.2.0/lib/
# echo $LD_PRELOAD
/opt/gcc-6.2.0/lib64/libasan.so.3
# ulimit -v
unlimited

Then I make the main.c

# cat main.c
int main()
{
int a[2] = {0, 1};
int b = a[2];
return 0;
}

compile like this:

#/opt/gcc-6.2.0/bin/gcc -fsanitize=address -ggdb -o main main.c

And finally I GOT:

# /opt/gcc-6.2.0/bin/gcc -fsanitize=address -ggdb -o main main.c

=================================================================
==27977==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 120 byte(s) in 8 object(s) allocated from:
#0 0x7f7037c9edd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x108f3a7 in xmalloc ../../libiberty/xmalloc.c:148

Direct leak of 32 byte(s) in 4 object(s) allocated from:
#0 0x7f7037c9edd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x108f3a7 in xmalloc ../../libiberty/xmalloc.c:148
#2 0x1ffffffffffffff ()

Direct leak of 14 byte(s) in 2 object(s) allocated from:
#0 0x7f7037c9edd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x108f3a7 in xmalloc ../../libiberty/xmalloc.c:148
#2 0x60800000289f ()

Direct leak of 8 byte(s) in 1 object(s) allocated from:
#0 0x7f7037c9edd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x108f3a7 in xmalloc ../../libiberty/xmalloc.c:148
#2 0x60400000ac0f ()

Direct leak of 7 byte(s) in 1 object(s) allocated from:
#0 0x7f7037c9edd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x108f3a7 in xmalloc ../../libiberty/xmalloc.c:148
#2 0x10001ffff ()

SUMMARY: AddressSanitizer: 181 byte(s) leaked in 16 allocation(s).

=================================================================
==27976==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 247 byte(s) in 4 object(s) allocated from:
#0 0x7f9a3c537dd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x466d97 in xmalloc ../../libiberty/xmalloc.c:148

Indirect leak of 16 byte(s) in 1 object(s) allocated from:
#0 0x7f9a3c537dd8 in __interceptor_malloc ../../../../libsanitizer/asan/asan_malloc_linux.cc:62
#1 0x466d97 in xmalloc ../../libiberty/xmalloc.c:148

SUMMARY: AddressSanitizer: 263 byte(s) leaked in 5 allocation(s).

[chefmax]

This happens because you preload ASan library to GCC and it detects leaks there (AFAIK those are known and ignored in community). Why do you need LD_PRELOAD at all? To run your binary (main) under ASan it's simply enough to compile it with -fsanitize=address flag.

[yangluoshen]

@chefmax Thanks for response
I unset LD_PRELOAD, I get the error following:

# export LD_PRELOAD=
# echo $LD_PRELOAD

# /opt/gcc-6.2.0/bin/gcc  -fsanitize=address -ggdb -o main main.c
# ./main
==92213==ASan runtime does not come first in initial library list; you should either link runtime to your application or manually preload it with LD_PRELOAD.

[yangluoshen]

Ha~ I found I works while I set LD_PRELOAD before run ./main and after compile main.c, like following:

# export LD_PRELOAD=
# /opt/gcc-6.2.0/bin/gcc  -fsanitize=address -ggdb -o main main.c
# export LD_PRELOAD=/opt/gcc-6.2.0/lib64/libasan.so.3
# ./main
=================================================================
==100519==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7fff8b699c38 at pc 0x000000400967 bp 0x7fff8b699bf0 sp 0x7fff8b699be8
READ of size 4 at 0x7fff8b699c38 thread T0
    #0 0x400966 in main /usr1/Fizz/up/mycode/workspace/test/gcc/main.c:4
    #1 0x7f66b4788c35 in __libc_start_main (/lib64/libc.so.6+0x1ec35)
    #2 0x400768  (/usr1/Fizz/up/mycode/workspace/test/gcc/main+0x400768)

Address 0x7fff8b699c38 is located in stack of thread T0 at offset 40 in frame
    #0 0x4008b7 in main /usr1/Fizz/up/mycode/workspace/test/gcc/main.c:2

@chefmax , Thank you really!