Re: [Ksummit-discuss] [TECH TOPIC] seccomp feature development

On Wed, May 20, 2020 at 11:27:03AM -0700, Linus Torvalds wrote:
> Don't make this some kind of abstract conceptual problem thing.
> Because it's not.

I have no intention of making this abstract (the requests for expanding
seccomp coverage have been for only a select class of syscalls, and
specifically clone3 and openat2) nor more complicated than it needs to be
(I regularly resist expanding the seccomp BPF dialect into eBPF).

> So details, please.

We've been discussing it all here:
https://lore.kernel.org/lkml/202005181120.971232B7B@keescook/

The example given in the thread was dealing with things like clone3's
struct clone_args's set_tid member, which is a pointer to a dynamically
sized array.

Things seccomp is NOT expected to introspect due to complexity would be
stuff like the bpf() syscall.

Perhaps the question is "how deeply does seccomp need to inspect?"
and maybe it does not get to see anything beyond just the "top level"
struct (i.e. struct clone_args) and all pointers within THAT become
opaque? That certainly simplifies the design.

-- 
Kees Cook
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