Disable and re-enable address space layout randomization only for myself

Question

I would like to disable address space layout randomization (ASLR) on my system (Ubuntu Gnu/Linux 2.6.32-41-server), but, if I use

sysctl -w kernel.randomize_         


        

Answer 1

The best way to disable locally the ASLR on a Linux-based system is to use processes personality flags. The command to manipulate personality flags is setarch with

-R, --addr-no-randomize

Disables randomization of the virtual address space (turns on ADDR_NO_RANDOMIZE).

Here is how to proceed:

$> setarch $(uname -m) -R /bin/bash

This command runs a shell in which the ASLR has been disabled. All descendants of this process will inherit of the personality flags of the father and thus have a disabled ASLR. The only way to break the inheritance of the flags would be to call a setuid program (it would be a security breach to support such feature).

Note that the uname -m is here to not hard-code the architecture of your platform and make this command portable.

Answer 2

The documentation for the randomize_va_space sysctl setting is in Documentation/sysctl/kernel.txt in the kernel source tree. Basically,

0 - Turn the process address space randomization off.

1 - Make the addresses of mmap base, stack and VDSO page randomized.

2 - Additionally enable heap randomization.