linux-hardening - Re: [PATCH 5/6] KEY: Apply PKEY_ENFORCE

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Date:   Tue, 16 May 2023 16:23:55 -0700
From:   Dave Hansen <dave.hansen@...el.com>
To:     jeffxu@...omium.org, luto@...nel.org, jorgelo@...omium.org,
        keescook@...omium.org, groeck@...omium.org, jannh@...gle.com,
        sroettger@...gle.com
Cc:     akpm@...ux-foundation.org, jeffxu@...gle.com,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-mm@...ck.org, linux-hardening@...r.kernel.org
Subject: Re: [PATCH 5/6] KEY: Apply PKEY_ENFORCE_API to munmap

On 5/15/23 06:05, jeffxu@...omium.org wrote:
> From: Jeff Xu <jeffxu@...gle.com>
> 
> This patch enables PKEY_ENFORCE_API for the munmap
> syscall.

The basic problem here is how we know when the set of syscalls that are
patched here is good enough and how we catch future functionality that
might need to be captured as well.

This mechanism really needs to be able to defend against *any* changes
to the address space.  I assume that folks are using syscall filtering
to prevent new syscalls from causing havoc, but is there anything that
can be done for, say, things like madvise()?  I bet it was harmless for
a long time until MADV_DONTNEED showed up and made it able to
effectively zero memory.