#43 test failure because of a use-after-free

[Agostino Sarubbo]

Our Gentoo Tinderbox reported a test failure at bug 914173

By looking at test-suite.log I can see:

==103==ERROR: AddressSanitizer: heap-use-after-free on address 0x604000000010 at pc 0x5575c34a16a4 bp 0x7ffc388e3c40 sp 0x7ffc388e3410
WRITE of size 8 at 0x604000000010 thread T0
    #0 0x5575c34a16a3 in __asan_memset (/var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/.libs/hmac_test+0xb76a3)
    #1 0x7f7a572d2e90 in mutils_memset /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/lib/stdfns.c
    #2 0x5575c34dcc14 in main /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/hmac_test.c:79:2
    #3 0x7f7a56e23c89  (/lib64/libc.so.6+0x23c89)
    #4 0x7f7a56e23d44 in __libc_start_main (/lib64/libc.so.6+0x23d44)
    #5 0x5575c34083b0 in _start (/var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/.libs/hmac_test+0x1e3b0)

0x604000000010 is located 0 bytes inside of 33-byte region [0x604000000010,0x604000000031)
freed by thread T0 here:
    #0 0x5575c34a1f56 in free (/var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/.libs/hmac_test+0xb7f56)
    #1 0x5575c34dcc05 in main /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/hmac_test.c:75:2
    #2 0x7f7a56e23c89  (/lib64/libc.so.6+0x23c89)

previously allocated by thread T0 here:
    #0 0x5575c34a21fe in __interceptor_malloc (/var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/.libs/hmac_test+0xb81fe)
    #1 0x7f7a572d634f in mutils_malloc /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/lib/stdfns.c:90:8
    #2 0x7f7a572d634f in mutils_asciify /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/lib/stdfns.c:605:25
    #3 0x5575c34dcbcf in main /var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/hmac_test.c:60:8
    #4 0x7f7a56e23c89  (/lib64/libc.so.6+0x23c89)

SUMMARY: AddressSanitizer: heap-use-after-free (/var/tmp/portage/app-crypt/mhash-0.9.9.9-r3/work/mhash-0.9.9.9/src/.libs/hmac_test+0xb76a3) in __asan_memset
Shadow bytes around the buggy address:
  0x603ffffffd80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x603ffffffe00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x603ffffffe80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x603fffffff00: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x603fffffff80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x604000000000: fa fa[fd]fd fd fd fd fa fa fa fa fa fa fa fa fa
  0x604000000080: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x604000000100: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x604000000180: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x604000000200: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x604000000280: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
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
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  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
==103==ABORTING

I didn't look deeply into this issue so I don't know if the bug is in the unittest itself or in the involed libraries/daemons, if so please check for any security implications.
If I can do further, please let me know.