On 12/16/21 08:31, Christian Brauner wrote:
On Thu, Dec 16, 2021 at 01:50:27PM +0100, Christian Brauner wrote:
On Thu, Dec 16, 2021 at 12:43:09AM -0500, Stefan Berger wrote:
This patch also introduces usage of CAP_MAC_ADMIN to allow access to the
IMA policy via reduced capabilities. We would again later on use this
capability to allow users to set file extended attributes for IMA appraisal
support.
My tree with these patches is here:
git fetch https://github.com/stefanberger/linux-ima-namespaces v5.15+imans.v7.posted
Regards,
Stefan
v7:
- Dropped 2 patches related to key queues; using &init_ima_ns for all calls
from functions related to key queues where calls need ima_namespace
- Moved ima_namespace to security/integrity/ima/ima.h
- Extended API descriptions with ns parameter where needed
- Using init_ima_ns in functions related to appraisal and xattrs
- SecurityFS: Using ima_ns_from_file() to get ns pointer
- Reformatted to 80 columns per line
Since we're starting to be fairly along I would ask you to please write
detailed commit messages for the next revision.
I would also like to see all links for prior versions of this patchset
in the commit message since the discussion has been fairly extensive so
for this series it makes a lot of sense. So something like:
Link: https://lore.kernel.org/r/$MSGID (v1)
Link: https://lore.kernel.org/r/$MSGID (v2)
Link: https://lore.kernel.org/r/$MSGID (v3)
Link: https://lore.kernel.org/r/$MSGID (v4)
Link: https://lore.kernel.org/r/$MSGID (v5)
Link: https://lore.kernel.org/r/$MSGID (v6)
Link: https://lore.kernel.org/r/$MSGID (v7)
Signed-off-by: meh
Signed-off-by: mih
Signed-off-by: muh
I find that extremely pleasant in case we need to revisit things later.
(Technically you can get the same by searching lore via the final link
but I find it be pretty pleasing to just copy+paste directly from the
commit message to the discussion for the earlier patch.)
So I looked through the series from a high-level view for once and I
would like to change how it is currently structured.
Currently, it looks a lot like you end up with a half-namespaced ima if
you compile and run a kernel in the middle of this patch series. Not
just is this asking for semantic chaos if we need to debug something it
also makes bisection a giant pain later.
In addition, the fact that you need a hack like
+struct ima_namespace {
+ int avoid_zero_size;
in the first patch is another good sign that this should be restructured.
Here's how I would prefer to see this done. I think we should organize
this in three big chunks (bullet points are not meant to signify
individual patches):
1. namespace securityfs
This patch is thematically standalone and should move to the
beginning of the series.
I would strongly recommend to fold patch 9 and 10 into a single patch
and add a lengthy explanation. You should be able to recycle a lof of
stuff I wrote in earlier reviews.
2. Introduce struct ima_namespace and pass it through to all callers:
- introduce struct ima_namespace
- move all the relevant things into this structure (this also avoids
the "avoid_zero_size" hack).
Before I start any move and don't get it right:
Is this to be done like in the current set of patches in those steps
where one thing is moved after another?
- define, setup, and expose init_ima_ns
We do this alongside the move of the individual pieces into
ima_namesapce as is done across the patches now? Most of those 'move'
patches haven't received much feedback so far.
- introduce get_current_ns() and always have it return &init_ima_ns for now
- replace all accesses to global variables to go through &init_ima_ns
And not pass get_current_ns() down from the top level and access the
right away via ns->foobar but use init_ima_ns.foobar instead?
- add new infrastructure you'll need later on
Bonus is that you can extend all the functions that later need access
to a specific ima namespace to take a struct ima_namespace * argument
and pass down &init_ima_ns down (retrieved via get_current_ns()). This
will make the actual namespace patch very easy to follow.
I am wondering how this new series is going to relate to the existing
series and the links you suggest be added on a per patch basis? How much
of the existing patches can be preserved?
3. namespace ima
- add a new entry for struct ima_namespace to struct user_namespace
- add creation helpers, kmem cache etc.
- create files in securityfs per ns
This way at all points in the series we have clearly defined semantics
where ima namespacing is either fully working or fully not working and
the switch is atomic in the patch(es) part of 3.
The existing series tried this by enabling IMA namespacing support when
SecurityFS is enabled... Is that also the last step then in what you
suggest?
