[PATCH] evm: Correct inode_init_security hooks behaviors

[Mimi Zohar]

On Tue, 2022-10-25 at 08:06 -0700, Casey Schaufler wrote:
> On 10/25/2022 7:21 AM, Mimi Zohar wrote:
> > On Tue, 2022-10-25 at 15:33 +0200, Nicolas Bouchinet wrote:
> >>> Agreed, independently as to whether BPF defines a security xattr, if
> >>> two LSMs initialize security xattrs, then this change is needed.  Are
> >>> there any other examples?
> >> I think that in its current state the kernel cannot load two LSM capable of xattr
> >> initialization as they are all defined with the `LSM_FLAG_EXCLUSIVE` flag set.
> >> But I may be unaware of other LSM in development stage.
> > Casey, Paul, can we get confirmation on this?
> 
> I'm working really hard to eliminate LSM_FLAG_EXCLUSIVE. Dealing with
> multiple security modules initializing security xattrs has been in the
> stacking patch sets that have been in review for years now. So no,
> you can't wave the problem away by pointing at LSM_FLAG_EXCLUSIVE.

Please note that the original problem being addressed by this patch
will be addressed by Roberto's BPF patch.   The question here was
whether this addresses an existing bug, other than BPF, or a future
one, and whether it needs to be backported.

>From your response, initializing multiple security xattrs is not an
issue at the moment so it doesn't need to be backported.  Whether this
patch should be upstreamed with the LSM stacking patch set is a
separate question.

> 
> >>> (nit: I understand the line size has generally been relaxed, but for
> >>> IMA/EVM I would prefer it to be remain as 80 chars.)
> >>>
> >> No problem, will change it !
> >>
> >> I'll take time to run few tests with BPF and send a patch v3 with new changes.
> > Since Roberto's patches will address the BPF bug(s), is this a fix for
> > a real bug or a possbile future one.   Cc'ing stable might not be
> > necessary.

-- 
thanks,

Mimi