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

linux bash aslr virtual-address-space sysctl
Amittai Aviram picture Amittai Aviram · Jun 28, 2012 · Viewed 19.8k times · Source

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_va_space=0

the change would affect all users on the system, I presume. (Is this true?) How can I limit the effects of disabling ASLR to myself as a user only, or only to the shell session in which I invoke the command to disable?

BTW, I see that my system's current (default) setting is

kernel.randomize_va_space = 2

Why 2 and not 1 or 3? Where can I find documentation about the numerical values of /proc/sys settings, their ranges, and their meanings? Thanks!

Answer

perror picture perror · Feb 12, 2014

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.

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