当我学习pwn时，使用gdb调试，但汇编返回失败

Question

I'm learning pwn about stack overflow. I use gdb to debug a linux elf file.

Elf binary only turns on NX.

I execute stack overflow successfully.

But when execute

leave  
ret

I meet a error.

First arrived leave

you can see

step

error shows

Cannot access memory at address 0x8

I do not access memory at 0x8 . Now $rbp is 0x0 , ubuntu check $rbp+0x8 when ret execute? why this happend?

My Environment

uname -a
Linux ubuntu 4.4.0-142-generic #168~14.04.1-Ubuntu SMP Sat Jan 19 11:26:28 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux

Answer 1

This can be because the instruction pointer points to 0x8 when you are overflowing the buffer. So the program tries to get to that location but there is no such location in the memory allocated for the binary. It would be better if you tell what the buffer size was and what was the amount of junk that you gave.

Thank You