Question

I’m working on a school project, and basically we’re trying to learn about stack overflows. Some sample code that I’m working on is basically: (trimmed down)

char test[10];
int i;
for (i=0;i < 10000;i++) {
    test[i] = 'a';
}

When I compile this with gcc, everything works all fine and dandy. Gcc automatically protects the stack and never lets it overflow outrageously. Now, if I try to use gcc -fno-stack-protector…. the exact same program runs. I even do a diff on the assembly files (the -S option) and they are identical. What gives? I searched through the man pages and there was no mention of the -fno-stack option… Everything online points to the -fno-stack-protector option, but I have not been able to recreate anything at all…

Thank you in advance for your help. 🙂

Answer 1

Are you sure? Mine gives (iff stack guard not disabled):

.L2:
        cmpl    $9999, -36(%rbp)
        jle     .L3
        movq    -8(%rbp), %rdx
        xorq    %fs:40, %rdx
        je      .L5
        call    __stack_chk_fail

from

int test() {
char test[10];
int i;
for (i=0;i < 10000;i++) {
  test[i] = 'a';
 }
}