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From: Janne Karhunen <janne.karhunen@gmail.com>
To: Eric Biggers <ebiggers@kernel.org>
Cc: linux-integrity@vger.kernel.org,
	linux-security-module@vger.kernel.org,
	Mimi Zohar <zohar@linux.ibm.com>,
	linux-mm@kvack.org, viro@zeniv.linux.org.uk,
	Konsta Karsisto <konsta.karsisto@gmail.com>
Subject: Re: [PATCH 1/3] ima: keep the integrity state of open files up to date
Date: Mon, 16 Sep 2019 14:45:56 +0300
Message-ID: <CAE=NcrbaJD4CaUvg1tmNSSKjkG-EizNM7GUaztA0=fiUCo03Cg@mail.gmail.com> (raw)
In-Reply-To: <20190915202433.GC1704@sol.localdomain>

On Sun, Sep 15, 2019 at 11:24 PM Eric Biggers <ebiggers@kernel.org> wrote:

> > > This still doesn't make it crash-safe.  So why is it okay?
> >
> > If Android is the load, this makes it crash safe 99% of the time and
> > that is considerably better than 0% of the time.
> >
>
> Who will use it if it isn't 100% safe?

I suppose anyone using mutable data with IMA appraise should, unless
they have a redundant power supply and a kernel that never crashes. In
a way this is like asking if the ima-appraise should be there for
mutable data at all. All this is doing is that it improves the crash
recovery reliability without taking anything away.

Anyway, I think I'm getting along with my understanding of the page
writeback slowly and the journal support will eventually be there at
least as an add-on patch for those that want to use it and really need
the last 0.n% reliability. Note that even without that patch you can
build ima-appraise based systems that are 99.999% reliable just by
having the patch we're discussing here. Without it you would be orders
of magnitude worse off. All we are doing is that we give it a fairly
good chance to recover instead of giving up without even trying.

That said, I'm not sure the 100% crash recovery is ever guaranteed in
any Linux system. We just have to do what we can, no?


--
Janne

  reply index

Thread overview: 14+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-09-02  9:45 Janne Karhunen
2019-09-02  9:45 ` [PATCH 2/3] ima: update the file measurement on truncate Janne Karhunen
2019-09-08 15:38   ` Mimi Zohar
2019-09-02  9:45 ` [PATCH 3/3] ima: update the file measurement on writes Janne Karhunen
2019-09-08 17:07   ` Mimi Zohar
2019-09-02 11:31 ` [PATCH 1/3] ima: keep the integrity state of open files up to date kbuild test robot
2019-09-02 12:57 ` kbuild test robot
2019-09-08 16:35 ` Mimi Zohar
2019-09-09 21:39 ` Eric Biggers
2019-09-10  7:04   ` Janne Karhunen
2019-09-15 20:24     ` Eric Biggers
2019-09-16 11:45       ` Janne Karhunen [this message]
2019-09-17  4:23         ` Eric Biggers
2019-09-17  7:24           ` Janne Karhunen

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