Groups | Search | Server Info | Keyboard shortcuts | Login | Register [http] [https] [nntp] [nntps]

Groups > linux.kernel > #1405195

Re: [PATCH] doc: self-protection: provide initial details

Show all headers | View raw

On Mon, 16 May 2016, Kees Cook wrote:

> +#### Segregation of kernel memory from userspace memory
> +
> +The kernel must never execute userspace memory. The kernel must also never
> +access userspace memory without explicit expectation to do so. These
> +rules can be enforced either by support of hardware-based restrictions
> +(x86's SMEP/SMAP, ARM's PXN/PAN) or via emulation (ARM's Memory Domains).
> +By blocking userspace memory in this way, execution and data parsing
> +cannot be passed to trivially-controlled userspace memory, forcing
> +attacks to operate entirely in kernel memory.

One caveat is that there may be ways to bypass these protections, e.g. via 
aliased (direct mapped) memory.

I'd also note that some platforms have separate kernel and memory spaces, 
like Sparc.


> +To protect against even privileged users, systems may need to either
> +disable module loading entirely (e.g. monolithic kernel builds or
> +modules_disabled sysctl), or provide signed modules (e.g.
> +CONFIG_MODULE_SIG_FORCE, or dm-crypt with LoadPin), to keep from having
> +oot load arbitrary kernel code via the module loader interface.

Or utilize an appropriate MAC policy.



-- 
James Morris
<jmorris@namei.org>

Back to linux.kernel | Previous | Next — Previous in thread | Find similar | Unroll thread

Thread

[PATCH] doc: self-protection: provide initial details Kees Cook <keescook@chromium.org> - 2016-05-17 04:30 +0200
  Re: [kernel-hardening] [PATCH] doc: self-protection: provide initial  details Greg KH <greg@kroah.com> - 2016-05-17 04:40 +0200
  Re: [PATCH] doc: self-protection: provide initial details Randy Dunlap <rdunlap@infradead.org> - 2016-05-17 17:40 +0200
  Re: [PATCH] doc: self-protection: provide initial details Jonathan Corbet <corbet@lwn.net> - 2016-05-18 00:30 +0200
    Re: [PATCH] doc: self-protection: provide initial details Kees Cook <keescook@chromium.org> - 2016-05-18 03:50 +0200
  Re: [PATCH] doc: self-protection: provide initial details James Morris <jmorris@namei.org> - 2016-05-23 11:40 +0200

csiph-web