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Date: Tue, 20 Feb 2018 12:21:11 +1100
From: Dave Chinner <>
To: Kees Cook <>
Cc: Igor Stoppa <>,
	Matthew Wilcox <>,
	Randy Dunlap <>,
	Jonathan Corbet <>, Michal Hocko <>,
	Laura Abbott <>,
	Jerome Glisse <>,
	Christoph Hellwig <>,
	Christoph Lameter <>,
	linux-security-module <>,
	Linux-MM <>, LKML <>,
	Kernel Hardening <>
Subject: Re: [RFC PATCH v16 0/6] mm: security: ro protection for dynamic data

On Mon, Feb 12, 2018 at 03:32:36PM -0800, Kees Cook wrote:
> On Mon, Feb 12, 2018 at 8:52 AM, Igor Stoppa <> wrote:
> > This patch-set introduces the possibility of protecting memory that has
> > been allocated dynamically.
> >
> > The memory is managed in pools: when a memory pool is turned into R/O,
> > all the memory that is part of it, will become R/O.
> >
> > A R/O pool can be destroyed, to recover its memory, but it cannot be
> > turned back into R/W mode.
> >
> > This is intentional. This feature is meant for data that doesn't need
> > further modifications after initialization.
> This series came up in discussions with Dave Chinner (and Matthew
> Wilcox, already part of the discussion, and others) at LCA. I wonder
> if XFS would make a good initial user of this, as it could allocate
> all the function pointers and other const information about a
> superblock in pmalloc(), keeping it separate from the R/W portions?
> Could other filesystems do similar things?

I wasn't cc'd on this patchset, (please use for
future postings) so I can't really say anything about it right
now. My interest for XFS was that we have a fair amount of static
data in XFS that we set up at mount time and it never gets modified
after that. I'm not so worried about VFS level objects (that's a
much more complex issue) but there is a lot of low hanging fruit in
the XFS structures we could convert to write-once structures.


Dave Chinner

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