Description of problem:
The kernel doesn't fully honor the ADDR_NO_RANDOMIZE flag for processes that set
it, e.g. via setarch -R.

Although the general randomization from fs/binfmt_elf.c:randomize_stack_top() is
disabled, randomization is also applied to the stack alignment in
arch_align_stack(), e.g.:

unsigned long arch_align_stack(unsigned long sp)
{
        if (randomize_va_space)
                sp -= get_random_int() % 8192;
        return sp & ~0xf;
}

This must also be conditional on PF_RANDOMIZE/ADDR_NO_RANDOMIZE or it will lead
to stack randomization over an 8k range (less than normal but still a problem
for debugging some apps).

Version-Release number of selected component (if applicable):


How reproducible:
100%

Steps to Reproduce:
1. compile & repeatedly run the following test case:
    #include <stdio.h>
    #include <stdlib.h>

    int main(){
        void *a;
        a=malloc(sizeof(int));
        printf("%p %pn", &a, a);
    }
2. E.g.:

    for i in `seq 1 10`;do setarch x86_64 -R ./a.out ;done

Actual results:
$ for i in `seq 1 10`;do setarch x86_64 -R ./a.out ;done
0x7fffffffc378 0x601010
0x7fffffffdc48 0x601010
0x7fffffffbe28 0x601010
0x7fffffffde58 0x601010
0x7fffffffbe18 0x601010
0x7fffffffc0b8 0x601010
0x7fffffffbbb8 0x601010
0x7fffffffdc88 0x601010
0x7fffffffc478 0x601010
0x7fffffffc5e8 0x601010


Expected results:
$ for i in `seq 1 10`;do setarch x86_64 -R ./a.out ;done
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010
0x7fffffffe1b8 0x601010


Additional info:
Fixed upstream in commit c16b63e09d9d03158e0a92e961234e94c4862620:
Author: Andi Kleen <ak>
Date:   Tue Sep 26 10:52:28 2006 +0200

    [PATCH] i386/x86-64: Don't randomize stack top when no randomization
personality is set
    
    Based on patch from Frank van Maarseveen <frankvm>, but
    extended.
    
    Signed-off-by: Andi Kleen <ak>