ASan stack-buffer-overflow src/frompnm.c:144 in load_pnm

[fgeek]

libsixel-stack-buffer-overflow-frompnm.c-144-load_pnm.png.zip (SHA1: 5cff689656ceb17302920cd64d9a9327a8b41cd4)
Tested commit: 5db717d
Credit: Henri Salo

./bin/img2sixel -o test libsixel-stack-buffer-overflow-frompnm.c-144-load_pnm.png
=================================================================
==27027==ERROR: AddressSanitizer: stack-buffer-overflow on address 0x7ffd6433b3a0 at pc 0x7fe8afc95b44 bp 0x7ffd6433b1b0 sp 0x7ffd6433b1a8
READ of size 1 at 0x7ffd6433b3a0 thread T0
    #0 0x7fe8afc95b43 in load_pnm /home/hsalo/src/libsixel/src/frompnm.c:144
    #1 0x7fe8afc85446 in load_with_builtin /home/hsalo/src/libsixel/src/loader.c:801
    #2 0x7fe8afc927f8 in sixel_helper_load_image_file /home/hsalo/src/libsixel/src/loader.c:1352
    #3 0x7fe8afcb37de in sixel_encoder_encode /home/hsalo/src/libsixel/src/encoder.c:1734
    #4 0x564f3917bbab in main /home/hsalo/src/libsixel/converters/img2sixel.c:457
    #5 0x7fe8aee3a2e0 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x202e0)
    #6 0x564f3917bde9 in _start (/home/hsalo/builds/libsixel/5db717dfef6fa327cd4025e7352550f63d20699c/bin/img2sixel+0x2de9)

Address 0x7ffd6433b3a0 is located in stack of thread T0 at offset 352 in frame
    #0 0x7fe8afc92cff in load_pnm /home/hsalo/src/libsixel/src/frompnm.c:64

  This frame has 2 object(s):
    [32, 44) 'component'
    [96, 352) 'tmp' <== Memory access at offset 352 overflows this variable
HINT: this may be a false positive if your program uses some custom stack unwind mechanism or swapcontext
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: stack-buffer-overflow /home/hsalo/src/libsixel/src/frompnm.c:144 in load_pnm
Shadow bytes around the buggy address:
  0x10002c85f620: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002c85f630: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002c85f640: 00 00 00 00 00 00 00 00 f1 f1 f1 f1 00 04 f4 f4
  0x10002c85f650: f2 f2 f2 f2 00 00 00 00 00 00 00 00 00 00 00 00
  0x10002c85f660: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x10002c85f670: 00 00 00 00[f3]f3 f3 f3 00 00 00 00 00 00 00 00
  0x10002c85f680: 00 00 00 00 00 00 00 00 00 00 00 00 f1 f1 f1 f1
  0x10002c85f690: 04 f4 f4 f4 f2 f2 f2 f2 00 f4 f4 f4 f2 f2 f2 f2
  0x10002c85f6a0: 00 f4 f4 f4 f2 f2 f2 f2 00 f4 f4 f4 f2 f2 f2 f2
  0x10002c85f6b0: 00 f4 f4 f4 f2 f2 f2 f2 00 f4 f4 f4 f2 f2 f2 f2
  0x10002c85f6c0: 00 02 f4 f4 f2 f2 f2 f2 00 00 00 00 f2 f2 f2 f2
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
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==27027==ABORTING

[saitoha]

@fgeek Thanks for your reporting, I'll release fixes as soon as possible.