heap-buffer-overflow at WritePixel() in ngiflib.c:123

[Marsman1996]

Tested in Ubuntu 16.04, 64bit, ngiflib(master 3bb9980)

Triggered by
$ gif2tga $POC

POC file:
https://github.com/Marsman1996/pocs/blob/master/ngiflib/poc13-WritePixel-heapoverflow

ASAN info:

==122089==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x621000002500 at pc 0x55dc592dfd89 bp 0x7ffc11226c20 sp 0x7ffc11226c10
WRITE of size 4 at 0x621000002500 thread T0
    #0 0x55dc592dfd88 in WritePixel /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/ngiflib.c:123
    #1 0x55dc592dfd88 in DecodeGifImg /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/ngiflib.c:544
    #2 0x55dc592e1e3b in LoadGif /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/ngiflib.c:809
    #3 0x55dc592dcdc4 in main /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/gif2tga.c:95
    #4 0x7f29ccd05b96 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x21b96)
    #5 0x55dc592dc169 in _start (/home/ubuntu/Desktop/crashana/ngiflib/ngiflib/gif2tga+0x2169)

0x621000002500 is located 0 bytes to the right of 4096-byte region [0x621000001500,0x621000002500)
allocated by thread T0 here:
    #0 0x7f29cd1b3b50 in __interceptor_malloc (/usr/lib/x86_64-linux-gnu/libasan.so.4+0xdeb50)
    #1 0x55dc592e0a38 in LoadGif /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/ngiflib.c:627

SUMMARY: AddressSanitizer: heap-buffer-overflow /home/ubuntu/Desktop/crashana/ngiflib/ngiflib/ngiflib.c:123 in WritePixel
Shadow bytes around the buggy address:
  0x0c427fff8450: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8460: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8470: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8480: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x0c427fff8490: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x0c427fff84a0:[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84b0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84c0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84d0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84e0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c427fff84f0: 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
==122089==ABORTING

[miniupnp]

fixed by 37d939a