Hi Janne,
Thanks for your response, I didn't reply right away as I hadn't used mm
and vmarea via vfs_tmpfile before, so I wanted to read some code to
familiarize myself with it. Correct me if I am misunderstanding the
approach you mentioned, but in it, we would still lose the logs accross
kexec/cold boots as we do today, is that correct? It feels like this
approach would solely solve the issue where we can potentially run out
of memory for ima logs.
For the original approach, I have a prototype version that I intend to
send as an RFC soon (I will link you and it's based off of your original
RFC from late last year).
- Raphael
On 8/26/2020 7:12 AM, Janne Karhunen wrote:
Hi,
Come to think of it, there could be a MM trap though as I'm not sure
this has been done before. This new file vmarea would sit in the
kernel virtual memory area somewhere above the page_offset and the mm
code might assume that there is no need to look for dirty pages there
when running the PTE scan. But that shouldn't be more than one line
patch if that is the only trap..
--
Janne
On Wed, Aug 26, 2020 at 4:40 PM Janne Karhunen <janne.karhunen@xxxxxxxxx> wrote:
Hi,
Attached a variant of the patch from that time that only does the
element free and relies on the userspace reading the data.
The reason why I stopped working on this at the time was that below
was sufficient for my needs. However, after a discussion between Mimi
and myself (based on a suggestion by Amir Goldstein) we realized that
we could do something considerably more elegant through vfs_tmpfile.
It's also much more work.
The way this could probably work the best is if we would implement a
new allocator that would pull pages from a vmarea tied to a
vfs_tmpfile and the file could be opened by the kernel itself during
the ima init. Now if all the measurement list data blobs would be
allocated through this allocator the pages would never be permanently
resident in the kernel, they would only visit the memory for a while
when someone reads the data. If done this way the allocator probably
does not even need a 'free' and the mm code would do all the real work
pushing the data out.
The benefits would be that no-one would ever have to poll from
userspace (kernel does not depend on the userspace to work) and we
would never OOM because of IMA as long as the filesystem is writable.
Also we would never lose any data as long as the file system is
functioning.
Thoughts?
--
Janne
On Wed, Aug 26, 2020 at 11:14 AM Janne Karhunen
<janne.karhunen@xxxxxxxxx> wrote:
Hi Raphael,
Sorry I missed the reply. I'm not working on this right now, feel free
to grab. Please copy me with the results, thank you.
--
Janne
On Tue, Aug 18, 2020 at 12:30 AM Raphael Gianotti
<raphgi@xxxxxxxxxxxxxxxxxxx> wrote:
Hi Janne,
Subject: Re: [RFC] ima: export the measurement list when needed
Date: Wed, 18 Dec 2019 17:11:22 +0200
From: Janne Karhunen <janne.karhunen@xxxxxxxxx>
To: linux-integrity@xxxxxxxxxxxxxxx, Mimi Zohar <zohar@xxxxxxxxxxxxx>
CC: Ken Goldman <kgold@xxxxxxxxxxxxx>, david.safford@xxxxxxxxx,
monty.wiseman@xxxxxx
Hi,
Have in mind that below is the first trial draft that booted and
seemingly accomplished the task once, it was not really tested at all
yet. I will make a polished and tested version if people like the
concept.
Note that the code (almost) supports pushing and pulling of the
entries. This variant is a simple pull given that the list size is
above the defined limits. Pushing can be put in place if the recursion
with the list extend_list_mutex is cleared, maybe this could be done
via another patch later on when we have a workqueue for the export
task? The workqueue might be the best context for the export job since
clearing the list is a heavy operation (and it's not entirely correct
here AFAIK, there is no rcu sync before the template free).
-- Janne
On Wed, Dec 18, 2019 at 2:53 PM Janne Karhunen
<janne.karhunen@xxxxxxxxx> wrote:
Some systems can end up carrying lots of entries in the ima
measurement list. Since every entry is using a bit of kernel
memory, add a new Kconfig variable to allow the sysadmin to
define the maximum measurement list size and the location
of the exported list.
The list is written out in append mode, so the system will
keep writing new entries as long as it stays running or runs
out of space. File is also automatically truncated on startup.
Signed-off-by: Janne Karhunen <janne.karhunen@xxxxxxxxx>
---
security/integrity/ima/Kconfig | 10 ++
security/integrity/ima/ima.h | 7 +-
security/integrity/ima/ima_fs.c | 178 +++++++++++++++++++++++++++++
security/integrity/ima/ima_queue.c | 2 +-
4 files changed, 192 insertions(+), 5 deletions(-)
I've been looking into a solution to this same issue you started some
work on. I was wondering if you are still working on it. I was
considering taking your initial prototyping on this and extending it
into a final solution, but I wanted to reply here first and check if you
are currently working on this.
