익스를 성공 했는데 왜 sfp가 오염 되지 않을 때랑 오염 될 때 익스의 성공 여부가 갈리는지 궁금합니다

gdb-peda$ x/100x $rbp-0x20
0x7fffffffdf10: 0x0000000000000000 0x0000000000000000
0x7fffffffdf20: 0x0a41414141414141 0x0000000000000000
0x7fffffffdf30: 0x0000000000000001 0x00007ffff7df118a
0x7fffffffdf40: 0x0000000000000000 0x0000555555400a41
0x7fffffffdf50: 0x0000000100000000 0x00007fffffffe048
0x7fffffffdf60: 0x00007fffffffe048 0x5e137add835f357b