Out of bounds heap read in perform_disassembly

[hannob]

Script:
https://crashes.fuzzing-project.org/radare2-script-oob-heap-read-perform_disassembly
Contains string "pD@!"

Address Sanitizer:

==6312==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x602000016550 at pc 0x7fcdf1deb214 bp 0x7ffde4e8af80 sp 0x7ffde4e8af70
READ of size 4 at 0x602000016550 thread T0
    #0 0x7fcdf1deb213 in perform_disassembly /f/radare2/radare2/libr/core/disasm.c:1076
    #1 0x7fcdf1e0413f in r_core_print_disasm /f/radare2/radare2/libr/core/disasm.c:2267
    #2 0x7fcdf1c9f8f5 in cmd_print /f/radare2/radare2/libr/core/cmd_print.c:2142
    #3 0x7fcdf1d01462 in r_core_cmd_subst_i /f/radare2/radare2/libr/core/cmd.c:1574
    #4 0x7fcdf1c63499 in r_core_cmd_subst /f/radare2/radare2/libr/core/cmd.c:1081
    #5 0x7fcdf1c64633 in r_core_cmd /f/radare2/radare2/libr/core/cmd.c:1943
    #6 0x7fcdf1c674ec in r_core_cmd_lines /f/radare2/radare2/libr/core/cmd.c:1994
    #7 0x7fcdf1c676f4 in r_core_cmd_file /f/radare2/radare2/libr/core/cmd.c:2006
    #8 0x7fcdf1c6a496 in r_core_run_script /f/radare2/radare2/libr/core/cmd.c:373
    #9 0x4054e3 in main /f/radare2/radare2/binr/radare2/radare2.c:729
    #10 0x7fcdec1c5f9f in __libc_start_main (/lib64/libc.so.6+0x1ff9f)
    #11 0x409fae (/mnt/ram/r2/radare2+0x409fae)

0x602000016551 is located 0 bytes to the right of 1-byte region [0x602000016550,0x602000016551)
allocated by thread T0 here:
    #0 0x7fcdf23926f7 in malloc (/usr/lib/gcc/x86_64-pc-linux-gnu/4.9.2/libasan.so.1+0x576f7)
    #1 0x7fcdf1c9f832 in cmd_print /f/radare2/radare2/libr/core/cmd_print.c:2136

SUMMARY: AddressSanitizer: heap-buffer-overflow /f/radare2/radare2/libr/core/disasm.c:1076 perform_disassembly
Shadow bytes around the buggy address:
  0x0c047fffac50: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fffac60: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fffac70: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x0c047fffac80: fa fa fa fa fa fa fd fa fa fa fd fd fa fa 00 02
  0x0c047fffac90: fa fa 00 02 fa fa 00 02 fa fa fd fa fa fa fd fa
=>0x0c047fffaca0: fa fa fd fa fa fa 03 fa fa fa[01]fa fa fa 04 fa
  0x0c047fffacb0: fa fa 01 fa fa fa 04 fa fa fa 02 fa fa fa 01 fa
  0x0c047fffacc0: fa fa 05 fa fa fa 05 fa fa fa 05 fa fa fa fd fd
  0x0c047fffacd0: fa fa fd fd fa fa fd fa fa fa fd fd fa fa 06 fa
  0x0c047ffface0: fa fa fd fa fa fa 05 fa fa fa fd fa fa fa 06 fa
  0x0c047fffacf0: fa fa fd fa fa fa 06 fa fa fa 03 fa fa fa fd 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
  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
  Contiguous container OOB:fc
  ASan internal:           fe
==6312==ABORTING

[alvarofe]

Also fixed in #2856. Wait to be merged to test