From Bugzilla Helper:
User-Agent: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.4) Gecko/20030709

Description of problem:
A program which analyzes another running program wants to see the previous
behavior of mmap(0, ...) beginning its search for a free page frame at
TASK_UNMAPPED_BASE (0x40000000 typical).  Exec-shield randomizes the value to be
something larger than 0x00100000 instead.  This behavior is supposed to be
controlled by /proc/sys/kernel/exec-shield, but trying all four legal values [0,
1, 2, 3] has no observable effect: the address used for mmap(0, ...) is always
random > 0x00100000.



Version-Release number of selected component (if applicable):
kernel-2.4.21-1.1931.2.393.ent

How reproducible:
Always

Steps to Reproduce:
1. Run script (as root)
-----
#!/bin/bash
                                                                                
for j in 0 1 2 3
do
        echo; echo ===== $j
        echo $j >/proc/sys/kernel/exec-shield
        echo exec-shield = $(cat /proc/sys/kernel/exec-shield)
        cat /proc/self/maps
done
-----
2.
3.
    

Actual Results:  Shared libraries are seen at "random" addresses > 0x00100000;
output attached.

Expected Results:  One of those values for exec-shield should force the old
behavior of allocating page frames sequentially beginning at TASK_UNMAPPED_BASE
(typically 0x40000000 in 2.4.20, for example).

Additional info: # uname -a
Linux taroon 2.4.21-1.1931.2.393.ent #1 Wed Aug 13 21:38:34 EDT 2003 i686 athlon
i386 GNU/Linux