Linux : What is address space layout randomization in linux ?

Question

I came under a term "address space layout randomization" ? What is the meaning of it ?

Can any one give any example on it how it works and what happens in this feature ?

Answer 1

Address Space Layout Randomization is an exploit mitigation technique which randomizes the process’ memory space in order to prevent the attacker from finding the addresses of functions or peripherals. One require the address of these to exploit them successfully.

Now coming to Linux, ASLR is available in Linux from kernel 2.6.12 and is forced on every executable.

Linux ASLR can be configured through /proc/sys/kernel/randomize_va_space. Supported values are -

0 – No randomization.
1 – Only Shared libraries, stack, mmap(), VDSO and heap are randomized.
2 – Full randomization. Addition to point 1 memory managed through brk() is also randomized.

Comments

Thanks for reply...
But the reason behind asking question is what kind of randomization he is doing with the memory space and how it does and why it is required ?

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I think I have already answered why it is required, now coming to kind of randomization - the catch is without randomization is linear memory setting and easy to guess/find the location of function and if it is non predictable then it is not. (AFAIK the algo must be simple for the randomization).

By the way the same was adopted in windows based OSs too later.

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Okay thanks Tapesh