Description

heap-buffer-overflow in function inc at misc2.c:356:6

vim version

git log
commit ba43e76fcd5b2da57dbaa4d9a555793fe8ac344e (HEAD -> master, tag: v9.0.0747, origin/master, origin/HEAD)

Proof of Concept

# ./src/vim -u NONE -X -Z -e -s -S ./poc -c ':qa!'
=================================================================
==2826727==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60200000782f at pc 0x560f6f87732f bp 0x7ffda688e1f0 sp 0x7ffda688e1e8
READ of size 1 at 0x60200000782f thread T0
    #0 0x560f6f87732e in inc /root/vim/src/misc2.c:356:6
    #1 0x560f6f8ec068 in nv_put_opt /root/vim/src/normal.c:7375:3
    #2 0x560f6f8da200 in nv_brackets /root/vim/src/normal.c:4502:2
    #3 0x560f6f8b662b in normal_cmd /root/vim/src/normal.c:920:5
    #4 0x560f6f6c13f4 in exec_normal /root/vim/src/ex_docmd.c
    #5 0x560f6f6c06c7 in exec_normal_cmd /root/vim/src/ex_docmd.c:8816:5
    #6 0x560f6f6c06c7 in ex_normal /root/vim/src/ex_docmd.c:8734:6
    #7 0x560f6f69906a in do_one_cmd /root/vim/src/ex_docmd.c:2578:2
    #8 0x560f6f69906a in do_cmdline /root/vim/src/ex_docmd.c:990:17
    #9 0x560f6fab2430 in do_source_ext /root/vim/src/scriptfile.c:1667:5
    #10 0x560f6fab010c in do_source /root/vim/src/scriptfile.c:1811:12
    #11 0x560f6fab010c in cmd_source /root/vim/src/scriptfile.c:1163:14
    #12 0x560f6f69906a in do_one_cmd /root/vim/src/ex_docmd.c:2578:2
    #13 0x560f6f69906a in do_cmdline /root/vim/src/ex_docmd.c:990:17
    #14 0x560f6fe4c5d3 in exe_commands /root/vim/src/main.c:3135:2
    #15 0x560f6fe4c5d3 in vim_main2 /root/vim/src/main.c:781:2
    #16 0x560f6fe4998f in main /root/vim/src/main.c:432:12
    #17 0x7f0dc1335d8f  (/lib/x86_64-linux-gnu/libc.so.6+0x29d8f) (BuildId: 69389d485a9793dbe873f0ea2c93e02efaa9aa3d)
    #18 0x7f0dc1335e3f in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x29e3f) (BuildId: 69389d485a9793dbe873f0ea2c93e02efaa9aa3d)
    #19 0x560f6f3f51f4 in _start (/root/vim/src/vim+0x1c41f4) (BuildId: 2bd6897ad54c4face0a7fa43a2ad04d588a03e15)

0x60200000782f is located 1 bytes to the left of 2-byte region [0x602000007830,0x602000007832)
allocated by thread T0 here:
    #0 0x560f6f47803e in __interceptor_malloc (/root/vim/src/vim+0x24703e) (BuildId: 2bd6897ad54c4face0a7fa43a2ad04d588a03e15)
    #1 0x560f6f4b3247 in lalloc /root/vim/src/alloc.c:246:11

SUMMARY: AddressSanitizer: heap-buffer-overflow /root/vim/src/misc2.c:356:6 in inc
Shadow bytes around the buggy address:
  0x0c047fff8eb0: fa fa fd fa fa fa 01 fa fa fa 01 fa fa fa 01 fa
  0x0c047fff8ec0: fa fa fd fa fa fa fd fa fa fa fd fa fa fa fd fa
  0x0c047fff8ed0: fa fa 02 fa fa fa fd fa fa fa fd fa fa fa 02 fa
  0x0c047fff8ee0: fa fa 01 fa fa fa 01 fa fa fa 02 fa fa fa 01 fa
  0x0c047fff8ef0: fa fa 01 fa fa fa 06 fa fa fa fd fa fa fa 01 fa
=>0x0c047fff8f00: fa fa 01 fa fa[fa]02 fa fa fa fa fa fa fa fa fa
  0x0c047fff8f10: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8f20: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8f30: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8f40: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fff8f50: 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
==2826727==ABORTING

POC

Report of the Information Security Laboratory of Ocean University of China @OUC_ISLOUC @OUC_Blue_Whale