The following use-after-free condition has been encountered in FreeType while fuzzing Type42 fonts. It has been reproduced with the current version of freetype2 from master git branch, with a 64-bit build of the ftbench utility compiled with AddressSanitizer:

$ ftbench <file>

Attached is a POC file which triggers the condition.

=================================================================
==6948==ERROR: AddressSanitizer: heap-use-after-free on address 0x61f00000f07f at pc 0x524983 bp 0x7fffecb369f0 sp 0x7fffecb369e8
READ of size 2048 at 0x61f00000f07f thread T0
    #0 0x524982 in FT_Stream_TryRead freetype2/src/base/ftstream.c:182
    #1 0x82b879 in _bdf_readstream freetype2/src/bdf/bdflib.c:716
    #2 0x820895 in bdf_load_font freetype2/src/bdf/bdflib.c:2404
    #3 0x813c7a in BDF_Face_Init freetype2/src/bdf/bdfdrivr.c:364
    #4 0x4cc13e in open_face freetype2/src/base/ftobjs.c:1191
    #5 0x4c794b in FT_Open_Face freetype2/src/base/ftobjs.c:2123
    #6 0x7bc3ab in T42_Face_Init freetype2/src/type42/t42objs.c:300
    #7 0x4cc13e in open_face freetype2/src/base/ftobjs.c:1191
    #8 0x4c794b in FT_Open_Face freetype2/src/base/ftobjs.c:2123
    #9 0x4c5b58 in FT_New_Face freetype2/src/base/ftobjs.c:1254
    #10 0x491533 in get_face ft2demos-2.5.3/src/ftbench.c:705
    #11 0x48d748 in main ft2demos-2.5.3/src/ftbench.c:924

0x61f00000f07f is located 511 bytes inside of 3072-byte region [0x61f00000ee80,0x61f00000fa80)
freed by thread T0 here:
    #0 0x471e61 in free (ft2demos-2.5.3/bin/ftbench+0x471e61)
    #1 0xaf2b78 in ft_free freetype2/src/base/ftsystem.c:130
    #2 0x4b04a0 in ft_mem_free freetype2/src/base/ftutil.c:172
    #3 0xa9c898 in ps_table_release freetype2/src/psaux/psobjs.c:271
    #4 0x7cb3a3 in t42_loader_done freetype2/src/type42/t42parse.c:1203
    #5 0x7c6aa5 in T42_Open_Face freetype2/src/type42/t42objs.c:149
    #6 0x7ba9ab in T42_Face_Init freetype2/src/type42/t42objs.c:196
    #7 0x4cc13e in open_face freetype2/src/base/ftobjs.c:1191
    #8 0x4c794b in FT_Open_Face freetype2/src/base/ftobjs.c:2123
    #9 0x4c5b58 in FT_New_Face freetype2/src/base/ftobjs.c:1254
    #10 0x491533 in get_face ft2demos-2.5.3/src/ftbench.c:705
    #11 0x48d748 in main ft2demos-2.5.3/src/ftbench.c:924

previously allocated by thread T0 here:
    #0 0x472081 in __interceptor_malloc (ft2demos-2.5.3/bin/ftbench+0x472081)
    #1 0xaf265f in ft_alloc freetype2/src/base/ftsystem.c:74
    #2 0x526b21 in ft_mem_qalloc freetype2/src/base/ftutil.c:76
    #3 0x4aee0f in ft_mem_alloc freetype2/src/base/ftutil.c:55
    #4 0xae4c19 in reallocate_t1_table freetype2/src/psaux/psobjs.c:125
    #5 0xa9bc38 in ps_table_add freetype2/src/psaux/psobjs.c:205
    #6 0x7d0e34 in t42_parse_encoding freetype2/src/type42/t42parse.c:450
    #7 0x7cc130 in t42_load_keyword freetype2/src/type42/t42parse.c:1007
    #8 0x7ca971 in t42_parse_dict freetype2/src/type42/t42parse.c:1154
    #9 0x7c4df8 in T42_Open_Face freetype2/src/type42/t42objs.c:57
    #10 0x7ba9ab in T42_Face_Init freetype2/src/type42/t42objs.c:196
    #11 0x4cc13e in open_face freetype2/src/base/ftobjs.c:1191
    #12 0x4c794b in FT_Open_Face freetype2/src/base/ftobjs.c:2123
    #13 0x4c5b58 in FT_New_Face freetype2/src/base/ftobjs.c:1254
    #14 0x491533 in get_face ft2demos-2.5.3/src/ftbench.c:705
    #15 0x48d748 in main ft2demos-2.5.3/src/ftbench.c:924

SUMMARY: AddressSanitizer: heap-use-after-free freetype2/src/base/ftstream.c:182 FT_Stream_TryRead
Shadow bytes around the buggy address:
  0x0c3e7fff9db0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff9dc0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c3e7fff9dd0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9de0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9df0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
=>0x0c3e7fff9e00: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd[fd]
  0x0c3e7fff9e10: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9e20: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9e30: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9e40: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x0c3e7fff9e50: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
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
  Contiguous container OOB:fc
  ASan internal:           fe
==6948==ABORTING
 

asan_heap-uaf_5212ba_6256_cov_2018364181_genotyrs.t42 36.8 KB Download