Bug record: Stack smashing when parse some file about ropchain

[hwchen18546]

Before Error
$ x/8x $ebp-16
0xbffff288: 0xb7fc3440 0xb7fd9ff4 0x00000000 0x00000000
0xbffff298: 0xbffff2c8 0xb7fd78d8 0xb78c6008 0x0032522c

After
$ x/8x $ebp-16
0xbffff288: 0x00746572 0xb7fd9ff4 0x00000000 0x00000000
0xbffff298: 0xbffff2c8 0xb7fd78d8 0xb78c6008 0x0032522c

0xbffff288 stack guard cover 0x00746572 ('ret')

GDB
$ watch *0xbffff288
Old value = 0xb7fc3440
New value = 0xb7fc3400
rop_print_gadgets (binary=0xb78c6008 "\177ELF\001\001\001", binary_len=0x32522c) at rop.c:42
41 total_gadget++;
42 for (k = 0; k < j; k++)

Old value = 0xb7fc3400
New value = 0x746572
rop_print_gadgets (binary=0xb78c6008 "\177ELF\001\001\001", binary_len=0x32522c) at rop.c:50
49 strcat(gadget_string, "ret");
50 printf("0x0%x:\t%s\n", text_address + i, gadget_string);

gadget_string over define MaxGadgetLen 200
commit 1e714ae
Fix bug: gadget_string cover canary stack smashing