Re: [Tarantool-patches] [PATCH msgpack v1] test: correct buffer size to fix ASAN error

[Vladislav Shpilevoy <v.shpilevoy@tarantool.org>]

Hi! Thanks for the patch!

See 2 comments below.

On 20.08.2020 10:02, Alexander V. Tikhonov wrote:
> Found ASAN error:
> 
> [001] +    ok 206 - =================================================================
> [001] +==6889==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x604000000031 at pc 0x0000005a72e7 bp 0x7ffe47c30c80 sp 0x7ffe47c30c78
> [001] +WRITE of size 1 at 0x604000000031 thread T0
> [001] +    #0 0x5a72e6 in mp_store_u8 /tarantool/src/lib/msgpuck/msgpuck.h:258:1
> [001] +    #1 0x5a72e6 in mp_encode_uint /tarantool/src/lib/msgpuck/msgpuck.h:1768
> [001] +    #2 0x4fa657 in test_mp_print /tarantool/src/lib/msgpuck/test/msgpuck.c:957:16
> [001] +    #3 0x509024 in main /tarantool/src/lib/msgpuck/test/msgpuck.c:1331:2
> [001] +    #4 0x7f3658fd909a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2409a)
> [001] +    #5 0x41f339 in _start (/tnt/test/unit/msgpack.test+0x41f339)
> [001] +
> [001] +0x604000000031 is located 0 bytes to the right of 33-byte region [0x604000000010,0x604000000031)
> [001] +allocated by thread T0 here:
> [001] +    #0 0x4cace3 in malloc (/tnt/test/unit/msgpack.test+0x4cace3)
> [001] +    #1 0x4fa5db in test_mp_print /tarantool/src/lib/msgpuck/test/msgpuck.c:945:18
> [001] +    #2 0x509024 in main /tarantool/src/lib/msgpuck/test/msgpuck.c:1331:2
> [001] +    #3 0x7f3658fd909a in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x2409a)
> [001] +
> [001] +SUMMARY: AddressSanitizer: heap-buffer-overflow /tarantool/src/lib/msgpuck/msgpuck.h:258:1 in mp_store_u8
> [001] +Shadow bytes around the buggy address:
> [001] +  0x0c087fff7fb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [001] +  0x0c087fff7fc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [001] +  0x0c087fff7fd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [001] +  0x0c087fff7fe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [001] +  0x0c087fff7ff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
> [001] +=>0x0c087fff8000: fa fa 00 00 00 00[01]fa fa fa fa fa fa fa fa fa
> [001] +  0x0c087fff8010: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> [001] +  0x0c087fff8020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> [001] +  0x0c087fff8030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> [001] +  0x0c087fff8040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> [001] +  0x0c087fff8050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
> [001] +Shadow byte legend (one shadow byte represents 8 application bytes):
> [001] +  Addressable:           00
> [001] +  Partially addressable: 01 02 03 04 05 06 07
> [001] +  Heap left redzone:       fa
> [001] +  Freed heap region:       fd
> [001] +  Stack left redzone:      f1
> [001] +  Stack mid redzone:       f2
> [001] +  Stack right redzone:     f3
> [001] +  Stack after return:      f5
> [001] +  Stack use after scope:   f8
> [001] +  Global redzone:          f9
> [001] +  Global init order:       f6
> [001] +  Poisoned by user:        f7
> [001] +  Container overflow:      fc
> [001] +  Array cookie:            ac
> [001] +  Intra object redzone:    bb
> [001] +  ASan internal:           fe
> [001] +  Left alloca redzone:     ca
> 
> Invetigated the buffer size that was allocated - it was 33 bytes, but it

1. Invetigated -> Investigated.

> needed 34. The fix was to increase this buffer.
> 
> Part of tarantool/tarantool#4360
> ---
> 
> Github: https://github.com/tarantool/msgpuck/tree/avtikhon/gh-4360-fix-asan-error
> Issue: https://github.com/tarantool/tarantool/issues/4360
> 
>  test/msgpuck.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/test/msgpuck.c b/test/msgpuck.c
> index 2d9bcbf..6613234 100644
> --- a/test/msgpuck.c
> +++ b/test/msgpuck.c
> @@ -940,7 +940,7 @@ test_mp_print()
>  
>  	/* Test mp_snprint max nesting depth. */
>  	int mp_buff_sz = MP_PRINT_MAX_DEPTH * mp_sizeof_array(1) +
> -			 mp_sizeof_uint(1);
> +			 mp_sizeof_uint(1) + 1;

2. Better change to this:

	int mp_buff_sz = (MP_PRINT_MAX_DEPTH + 1) * mp_sizeof_array(1) +
			 mp_sizeof_uint(1);

To emphasize, that +1 comes from one another mp_encode_array(1).

>  	int exp_str_sz = 2 * (MP_PRINT_MAX_DEPTH + 1) + 3 + 1;
>  	char *mp_buff = malloc(mp_buff_sz);
>  	char *exp_str = malloc(exp_str_sz);