Re: RFC: seccomp-bpf support

On Wed, Aug 28, 2019 at 2:30 PM Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
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<snip>
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> (And, TBH, I'm still wondering why SELinux isn't the way to address this.)

Just going to address this one now. SELinux is an LSM and therefore
only makes decisions when LSM hooks are invoked, which are not 1:1 for
syscalls (not even close). Further, SELinux generally determines what
objects a subject can access and only implements capabilities because
it has to, to be non-bypassable.

Seccomp filtering is an orthogonal system to SELinux and LSMs in
general. We are already doing work to further restrict PG subprocesses
with SELinux via [1] and [2], but that doesn't address the unused,
high-risk, obsolete, etc syscall issue. A prime example is madvise()
which was a catastrophic failure that 1) isn't preventable by any LSM
including SELinux, 2) isn't used by PG and is therefore a good
candidate for a kill list, and 3) a clear win in the
dont-let-PG-be-a-vector-for-kernel-compromise arena.

We are using SELinux, we are also going to use this, they work together.