Re: [PATCH v10 26/27] ima: Limit number of policy rules in non-init_ima_ns

[Stefan Berger]

On 2/23/22 12:04, Mimi Zohar wrote:
> On Wed, 2022-02-23 at 11:37 -0500, Stefan Berger wrote:
> > On 2/23/22 10:38, Mimi Zohar wrote:
> > > On Tue, 2022-02-01 at 15:37 -0500, Stefan Berger wrote:
> > > > Limit the number of policy rules one can set in non-init_ima_ns to a
> > > > hardcoded 1024 rules. If the user attempts to exceed this limit by
> > > > setting too many additional rules, emit an audit message with the cause
> > > > 'too-many-rules' and simply ignore the newly added rules.
> > > This paragraph describes 'what' you're doing, not 'why'.  Please prefix
> > > this paragraph with a short, probably one sentence, reason for the
> > > change.
> > > > Switch the accounting for the memory allocated for IMA policy rules to
> > > > GFP_KERNEL_ACCOUNT so that cgroups kernel memory accounting takes effect.
> > > Does this change affect the existing IMA policy rules for init_ima_ns?
> > There's typically no cgroup for the int_ima_ns, so not effect on
> > init_ima_ns.
> >
> > Here's the updated text:
> >
> > Limit the number of policy rules one can set in non-init_ima_ns to a
> > hardcoded 1024 rules to restrict the amount of memory used for IMA's
> > policy.
> The question is "why" there should be a difference between the
> init_ima_ns and non-init_ima_ns cases.  Perhaps something like, "Only


Chistian had suggested it to not have the number of policy rules unbounded.


> host root with CAP_SYS_ADMIN may write init_ima_ns policy rules, but in
> the non-init_ima_ns case root in the namespace with CAP_MAC_ADMIN
> privileges may write IMA policy rules.  Limit the total number of IMA
> policy rules per namespace."

What does it have to do with CAP_SYS_ADMIN and CAP_MAC_ADMIN and why 
mention these here? It seem primarily a limit of number of rules to 
avoid huge kernel memory consumption in the case that a cgroup limit for 
memory was not set up.


> >   Ignore the added rules if the user attempts to exceed this
> > limit by setting too many additional rules.
> >
> > Switch the accounting for the memory allocated for IMA policy rules to
> > GFP_KERNEL_ACCOUNT so that cgroups kernel memory accounting takes effect.
> > This switch has no effect on the init_ima_ns.
> thanks,
>
> Mimi