infinite loop in shellcode

Question

I want to display an hello world from shellcode, c code is simple:

#include <stdio.h>

char shellcode[] = "\xeb\x17\x59\x31\xc0\xb0\x04\x31\xdb\x43\x31\xd2\xb2\x0f\xcd\x80\xb0\x01\xbb\x00\x00\x00\x00\xcd\x80\xe8\xe4\xff\xff\xff\x48\x65\x6c\x6c\x6f\x20\x73\x68\x65\x6c\x6c\x21\x0a\x0d";

int main(int argc, char **argv){

int (*func)();

func = (int (*)()) shellcode;

(int)(*func)();

return 0;
}

problem should be in the assembly file, here it is:

BITS 32
jmp short one

;write hello world on standard output
two:
pop ecx  ;i get string address
xor eax,eax 
mov al,4 
xor ebx,ebx
inc bl ;bl should be 1
xor edx,edx
mov dl,15
int 0x80

;exit with status 0
mov al,1
xor ebx,ebx
int 0x80

one:
call two
db "Hello shell!",0x0a,0x0d

code works good but does not exits after displaying "hello shell!", on the contrary it keeps displaying this sentence like in an infinite loop.

Answer 1

It seems that first int 0x80 returns the return value in eax. After that you set al to 1, but not eax.

So you should change your code to:

mov eax,1
xor ebx,ebx
int 0x80