CVE-2021-33480: Optical Character Recognition (GOCR) / Bugs

System info

Ubuntu X64, gcc (Ubuntu 5.5.0-12ubuntu1), gocr (latest jocr-dev 0.53-20200802)

Configure

CFLAGS="-g -fsanitize=address" LDFLAGS="-fsanitize=address" ./configure

Command line

./src/gocr -m 4 ./use-after-free-context_correction-pgm2asc-2817

AddressSanitizer output

================================================================= ==33563==ERROR: AddressSanitizer: heap-use-after-free on address 0x61a000001ea4 at pc 0x00000054552b bp 0x7ffde2563980 sp 0x7ffde2563978 READ of size 4 at 0x61a000001ea4 thread T0 #0 0x54552a in context_correction /home/seviezhou/AlphaFuzz/targets/jocr/src/pgm2asc.c:2817:39 #1 0x54a291 in pgm2asc /home/seviezhou/AlphaFuzz/targets/jocr/src/pgm2asc.c:3427:28 #2 0x518776 in main /home/seviezhou/AlphaFuzz/targets/jocr/src/gocr.c:350:5 #3 0x7f394175f83f in __libc_start_main /build/glibc-e6zv40/glibc-2.23/csu/…/csu/libc-start.c:291 #4 0x41a768 in _start (/home/seviezhou/AlphaFuzz/targets/gocr/src/gocr+0x41a768)

0x61a000001ea4 is located 36 bytes inside of 1376-byte region [0x61a000001e80,0x61a0000023e0) freed by thread T0 here: #0 0x4de7b8 in __interceptor_cfree.localalias.0 /home/seviezhou/llvm-6.0.0/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:76 #1 0x54c1a7 in free_box /home/seviezhou/AlphaFuzz/targets/jocr/src/box.c:122:3

previously allocated by thread T0 here: #0 0x4de978 in __interceptor_malloc /home/seviezhou/llvm-6.0.0/projects/compiler-rt/lib/asan/asan_malloc_linux.cc:88 #1 0x54bdc2 in malloc_box /home/seviezhou/AlphaFuzz/targets/jocr/src/box.c:96:24

SUMMARY: AddressSanitizer: heap-use-after-free /home/seviezhou/AlphaFuzz/targets/jocr/src/pgm2asc.c:2817:39 in context_correction Shadow bytes around the buggy address: 0x0c347fff8380: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff8390: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff83a0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff83b0: fd fd fd fd fd fd fd fd fd fd fd fd fa fa fa fa 0x0c347fff83c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa =>0x0c347fff83d0: fd fd fd fd[fd]fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff83e0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff83f0: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff8400: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff8410: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd 0x0c347fff8420: 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 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 ==33563==ABORTING