Re: Question: a module for wiping userspace RAM before shutdown/reboot/halt

[Christophe Leroy <christophe.leroy@csgroup.eu>]

Le 15/05/2025 à 15:30, Danill Klimuk a écrit :

> Hello everyone. I have received a request to write a Linux kernel module
> that will wipe any processes leftovers from userspace RAM during/before
> Linux kernel shutdown/reboot/halt sequences. The reason I am going to do
> it inside a module is to do it in a more deterministic way that does not
> depend on any processes. AFAIK Linux kernel does not have any other
> functionalities to wipe leftovers from RAM apart from the command line
> arguments "init_on_free" and "init_on_alloc" that results in memory
> poisoning only during memory allocation and memory deallocation. These
> arguments cause the kernel to clean processes memory several times
> during runtime, that is not deterministic because of processes
> non-deterministic behavior. Hence, I want to bring the memory wiping
> mechanism in one place and make it more deterministic. The question is:
> 
> Maybe the Linux kernel already have such functionalities implemented?

Linux memory management topics should be sent to linux-mm@kvack.org

> 
> Currently I am planning to implement the wiping process to be triggered
> by "reboot_notifier_callback", so to wipe RAM after PID 1 process
> finishes and no other processes are executing. I am looking forward to
> merging the module into Linux kernel upstream too.

What do you mean by 'wiping', do you mean 'clearing' ?

Can you explain the reason this is needed ?

Christophe