Heap buffer overflow

[clayton-shopify]

The following input demonstrates a crash:

d 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 < 0 - 1&.-- 0

This is a slight variation of the input in #3440, so it may be a related issue.

ASAN report:

==14624==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x61d00001de88 at pc 0x00010adf78ba bp 0x7fff54f6d850 sp 0x7fff54f6d848
WRITE of size 4 at 0x61d00001de88 thread T0
    #0 0x10adf78b9 in mrb_vm_exec vm.c:1164
    #1 0x10adef239 in mrb_vm_run vm.c:815
    #2 0x10ae20a59 in mrb_top_run vm.c:2573
    #3 0x10aeee7f5 in mrb_load_exec parse.y:5755
    #4 0x10aeef5c5 in mrb_load_file_cxt parse.y:5764
    #5 0x10ac8bcca in main mruby.c:232
    #6 0x7fffb4357254 in start (libdyld.dylib+0x5254)

0x61d00001de88 is located 8 bytes to the right of 2048-byte region [0x61d00001d680,0x61d00001de80)
allocated by thread T0 here:
    #0 0x10b02df87 in wrap_realloc (libclang_rt.asan_osx_dynamic.dylib+0x4af87)
    #1 0x10ad84fb5 in mrb_default_allocf state.c:60
    #2 0x10ad06468 in mrb_realloc_simple gc.c:201
    #3 0x10ad06b4e in mrb_realloc gc.c:215
    #4 0x10ad075c3 in mrb_malloc gc.c:236
    #5 0x10ad0765d in mrb_calloc gc.c:254
    #6 0x10ade6672 in stack_init vm.c:97
    #7 0x10ade35df in mrb_funcall_with_block vm.c:376
    #8 0x10ade2f57 in mrb_funcall_with_block vm.c:354
    #9 0x10ade2737 in mrb_funcall_argv vm.c:461
    #10 0x10acc9b35 in mrb_obj_new class.c:1425
    #11 0x10acee59d in mrb_exc_new_str error.c:32
    #12 0x10acf8bb7 in mrb_init_exception error.c:549
    #13 0x10ad29d90 in mrb_init_core init.c:41
    #14 0x10ad84f4e in mrb_open_core state.c:47
    #15 0x10ad8511c in mrb_open_allocf state.c:107
    #16 0x10ad850e7 in mrb_open state.c:99
    #17 0x10ac8aa47 in main mruby.c:172
    #18 0x7fffb4357254 in start (libdyld.dylib+0x5254)

SUMMARY: AddressSanitizer: heap-buffer-overflow vm.c:1164 in mrb_vm_exec
Shadow bytes around the buggy address:
  0x1c3a00003b80: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c3a00003b90: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c3a00003ba0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c3a00003bb0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c3a00003bc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
=>0x1c3a00003bd0: fa[fa]fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c3a00003be0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c3a00003bf0: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c3a00003c00: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c3a00003c10: fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd fd
  0x1c3a00003c20: 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
  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
==14624==ABORTING
Abort trap: 6

This issue was reported by https://hackerone.com/ssarong