stack-buffer-underflow in htmldoc

[Kaka201]

os: ubuntu 20.04
htmldoc version: master branch

command : ./htmldoc --webpage -f out.pdf ./poc.html

poc.zip

asan report

=================================================================
==100970==ERROR: AddressSanitizer: stack-buffer-underflow on address 0x7ffd98c936be at pc 0x000000605f03 bp 0x7ffd98c93690 sp 0x7ffd98c93688
READ of size 1 at 0x7ffd98c936be thread T0
    #0 0x605f02 in image_load_bmp(image_t*, _IO_FILE*, int, int) /home/ubuntu/fuzz/htmldocc/htmldoc/image.cxx:1089:12
    #1 0x602b94 in image_load /home/ubuntu/fuzz/htmldocc/htmldoc/image.cxx:831:14
    #2 0x53bc18 in write_image(_IO_FILE*, render_str*, int) /home/ubuntu/fuzz/htmldocc/htmldoc/ps-pdf.cxx:10305:5
    #3 0x5207fa in pdf_write_document(unsigned char*, unsigned char*, unsigned char*, unsigned char*, unsigned char*, unsigned char*, tree_str*, tree_str*) /home/ubuntu/fuzz/htmldocc/htmldoc/ps-pdf.cxx:2292:7
    #4 0x50c977 in pspdf_export /home/ubuntu/fuzz/htmldocc/htmldoc/ps-pdf.cxx:910:7
    #5 0x4e1663 in main /home/ubuntu/fuzz/htmldocc/htmldoc/htmldoc.cxx:1291:3
    #6 0x7ff2c1e7d0b2 in __libc_start_main /build/glibc-YbNSs7/glibc-2.31/csu/../csu/libc-start.c:308:16
    #7 0x41eadd in _start (/home/ubuntu/fuzz/htmldocc/htmldoc/htmldoc+0x41eadd)

Address 0x7ffd98c936be is located in stack of thread T0 at offset 30 in frame
    #0 0x6048ef in image_load_bmp(image_t*, _IO_FILE*, int, int) /home/ubuntu/fuzz/htmldocc/htmldoc/image.cxx:881

  This frame has 1 object(s):
    [32, 1056) 'colormap' (line 894) <== Memory access at offset 30 underflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-underflow /home/ubuntu/fuzz/htmldocc/htmldoc/image.cxx:1089:12 in image_load_bmp(image_t*, _IO_FILE*, int, int)
Shadow bytes around the buggy address:
  0x10003318a680: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a690: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a6a0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a6b0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a6c0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10003318a6d0: 00 00 00 00 f1 f1 f1[f1]00 00 00 00 00 00 00 00
  0x10003318a6e0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a6f0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a700: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a710: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10003318a720: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
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
  Shadow gap:              cc
==100970==ABORTING

[michaelrsweet]

[master f12b966] Fix BMP crash bug (Issue #444)

[Kaka201]

cve-2021-40985 has been assigned
report by luo likang of NSFOCUS TianJi team