lru_cache_test and hash_table_test fail AddressSanitizer

[jkuszmaul]

On v0.4.2 (018e74c), the following tests appear to fail with asan compiled with either gcc or clang:

test_hash_table_create_find
test_hash_table_string_create_find
test_hash_table_string_clean_up
test_hash_table_hash_overwrite
test_hash_table_hash_remove
test_hash_table_hash_clear_allows_cleanup
test_hash_table_byte_cursor_create_find
test_lru_cache_overflow_static_members
test_lru_cache_lru_ness_static_members
test_lru_cache_entries_cleanup
test_lru_cache_entries_cleanup
test_lru_cache_overwrite
test_lru_cache_element_access_members

Is this expected?

Sample failure:

=================================================================
==14==ERROR: AddressSanitizer: global-buffer-overflow on address 0x55e94a5be484 at pc 0x7f040beac27f bp 0x7fff0828f690 sp 0x7fff0828f688
READ of size 4 at 0x55e94a5be484 thread T0
    #0 0x7f040beac27e in hashlittle2 /proc/self/cwd/third_party/aws_c_common/include/aws/common/private/lookup3.inl:551:17
    #1 0x7f040beaad8e in aws_hash_c_string /proc/self/cwd/third_party/aws_c_common/source/hash_table.c:958:5
    #2 0x7f040bea8402 in s_hash_for /proc/self/cwd/third_party/aws_c_common/source/hash_table.c:58:26
    #3 0x7f040bea8402 in aws_hash_table_create /proc/self/cwd/third_party/aws_c_common/source/hash_table.c:528
    #4 0x55e94a51df85 in s_test_hash_table_create_find_fn /proc/self/cwd/third_party/aws_c_common/tests/hash_table_test.c:67:16
    #5 0x55e94a51d5a4 in s_aws_run_test_case /proc/self/cwd/third_party/aws_c_common/include/aws/testing/aws_test_harness.h:390:19
    #6 0x55e94a4c8ed3 in main /proc/self/cwd/bazel-out/k8-opt-asan/genfiles/third_party/aws_c_common/test_runner.c:708:20
    #7 0x7f040ac3d2e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
    #8 0x55e94a414465 in _start (/x2/home/james/.cache/bazel/_bazel_james/a4cb2cd708de4c2f2bdeacec8e67447d/execroot/com_peloton_tech/bazel-out/k8-opt-asan/bin/third_party/aws_c_common/all_tests+0xb3465)

0x55e94a5be484 is located 60 bytes to the left of global variable '<string literal>' defined in 'third_party/aws_c_common/tests/hash_table_test.c:26:37' (0x55e94a5be4c0) of size 8
  '<string literal>' is ascii string 'value 1'
0x55e94a5be487 is located 0 bytes to the right of global variable '<string literal>' defined in 'third_party/aws_c_common/tests/hash_table_test.c:23:33' (0x55e94a5be480) of size 7
  '<string literal>' is ascii string 'test 1'
SUMMARY: AddressSanitizer: global-buffer-overflow /proc/self/cwd/third_party/aws_c_common/include/aws/common/private/lookup3.inl:551:17 in hashlittle2
Shadow bytes around the buggy address:
  0x0abda94afc40: 00 07 f9 f9 f9 f9 f9 f9 00 00 00 03 f9 f9 f9 f9
  0x0abda94afc50: 00 00 00 06 f9 f9 f9 f9 00 00 00 00 00 01 f9 f9
  0x0abda94afc60: f9 f9 f9 f9 00 07 f9 f9 f9 f9 f9 f9 00 00 00 03
  0x0abda94afc70: f9 f9 f9 f9 00 00 00 01 f9 f9 f9 f9 00 00 02 f9
  0x0abda94afc80: f9 f9 f9 f9 00 00 00 00 00 07 f9 f9 f9 f9 f9 f9
=>0x0abda94afc90:[07]f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
  0x0abda94afca0: 07 f9 f9 f9 f9 f9 f9 f9 00 f9 f9 f9 f9 f9 f9 f9
  0x0abda94afcb0: 00 00 00 00 03 f9 f9 f9 f9 f9 f9 f9 00 00 00 00
  0x0abda94afcc0: 00 f9 f9 f9 f9 f9 f9 f9 04 f9 f9 f9 f9 f9 f9 f9
  0x0abda94afcd0: 00 00 00 00 f9 f9 f9 f9 00 00 00 00 f9 f9 f9 f9
  0x0abda94afce0: 00 00 00 00 00 f9 f9 f9 f9 f9 f9 f9 00 01 f9 f9
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07
  Heap left redzone:       fa
  Heap right redzone:      fb
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack partial redzone:   f4
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==14==ABORTING
================================================================================

[DmitriyMusatkin]

Yes, this is expected. Implementation is safe, but sanitizers do not like how memory is accessed. A little bit more info on it here - https://github.com/awslabs/aws-c-common/blob/main/include/aws/common/private/lookup3.inl#L500.
We've added some annotations on this method since then, so it should no longer be flagged by sanitizers.