Linux

This sounds like SELinux … just with less understanding.

The Linux kernel already has the infrastructure required for that. Heck, Android itself, including its permission system, is built atop the Linux kernel.

Making sandboxing the default instead of having to restrict programs.

What's missing for that is work on userspace software and app packaging. The kernel can't automatically know what a program should and shouldn't be allowed to do.

Some of that work has happened, like moving from X11, which really wasn't designed around sandboxing, to Wayland.

But a lot of it requires making a permission system the norm and creating a system such that software is normally distributed with restricted permissions and developers develop around that. Like, I can use firejail and disallow write access to parts of the filesystem or network access to a program, but there isn't a broad system of appropriate pre-created profiles that applications are distributed with and way to view this. We don't have a convention for an application-private space on disk and lack of access to most of the filesystem, which Android does and apps need to be written around.

IMHO, one of the largest jumps would be Valve doing this for Steam games

a lot of games are going to be amenable to being sandboxed, don't need broad access to the system, and are closed source. There are some issues there; for Windows binaries run under Proton, WINE wasn't originally written around being isolated, and the game developers writing the software are writing to a Windows API that aren't under the control of people on the Linux side of things.

I haven't poked at snaps much or their technical underpinnings, but my understanding is that the snap packages distribute apps in a sandboxed form, so that might be the closest Linux-native approach. I don't recall seeing an obvious set of permissions required a la Android package managers, though.

Look up "capabilities-based operating systems." They exist; Linux just isn't one.

Like microkernels, capabilities require certain core architecture designs that Linux doesn't have. Like all features, there are always tradeoffs: microkernels tend to be slower because of the message passing; capabilities based systems are harder to manage. Linux's design, for all it's popularity, is about a simple a kernel design as possible. And you see people making the same decisions now: X11 is inherently multi-user and network capable. Wayland eliminates both, because it makes things more simple.

Let the kernel do kernel job, chief. It aint a kernel no more if it does apps job.

Mainly because it's not the kernel's job. It provides abstractions to access the hardware, manages memory and manages processes, it doesn't care what userspace does that's userspace's problem.

The kernel is responsible for enforcing security policies, but not for writing them or discovering them. It doesn't know what an "app" is, or what a permission would look like.

It's the userspace that assigns labels to files and SELinux policies so that the kernel is programmed to know what the boundaries are. As an example, when you log in on a Linux computer, logind ends up assigning your user access to the keyboard, mouse, display and audio to your user and then starts your session and that's how you get access to those /dev nodes. If you switch user they're yanked away from you so the other user can use them without you snooping on it.

Userspace uses the kernel's features to implement the permission systems. That's basically what Flatpak does: leverage those kernel features to sandbox the application. And it works great and is effective.

Android also uses the Linux kernel and its features for its own sandbox and permission system too.

Generally, the kernel provides the tools for userspace to be able to do things, that's its purpose. For example all the OpenGL and Vulkan stuff is in userspace, not the kernel, the kernel doesn't know what Vulkan is and doesn't care. It mediates access to the GPU and reserving memory on it anf uploading code to it. The code comes from your GPU driver in userspace.

It exists, there's already selinux and apparmor.