[PATCH 23/28] security: Introduce LSM_ORDER_LAST

[Roberto Sassu]

On Tue, 2023-03-07 at 13:04 -0500, Stefan Berger wrote:
> 
> On 3/3/23 13:25, Roberto Sassu wrote:
> > From: Roberto Sassu <roberto.sassu at huawei.com>
> > 
> > Introduce LSM_ORDER_LAST, to satisfy the requirement of LSMs willing to be
> > the last, e.g. the 'integrity' LSM, without changing the kernel command
> > line or configuration.
> > 
> > As for LSM_ORDER_FIRST, LSMs with LSM_ORDER_LAST are always enabled and put
> > at the end of the LSM list in no particular order.
> > 
> 
> I think you should describe the reason for the change for LSM_ORDER_MUTABLE as well.

Right.

Thanks

Roberto

> > Signed-off-by: Roberto Sassu <roberto.sassu at huawei.com>
> > ---
> >   include/linux/lsm_hooks.h |  1 +
> >   security/security.c       | 12 +++++++++---
> >   2 files changed, 10 insertions(+), 3 deletions(-)
> > 
> > diff --git a/include/linux/lsm_hooks.h b/include/linux/lsm_hooks.h
> > index 21a8ce23108..05c4b831d99 100644
> > --- a/include/linux/lsm_hooks.h
> > +++ b/include/linux/lsm_hooks.h
> > @@ -93,6 +93,7 @@ extern void security_add_hooks(struct security_hook_list *hooks, int count,
> >   enum lsm_order {
> >   	LSM_ORDER_FIRST = -1,	/* This is only for capabilities. */
> >   	LSM_ORDER_MUTABLE = 0,
> > +	LSM_ORDER_LAST = 1,
> >   };
> >   
> >   struct lsm_info {
> > diff --git a/security/security.c b/security/security.c
> > index 322090a50cd..24f52ba3218 100644
> > --- a/security/security.c
> > +++ b/security/security.c
> > @@ -284,9 +284,9 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
> >   		bool found = false;
> >   
> >   		for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
> > -			if (lsm->order == LSM_ORDER_MUTABLE &&
> > -			    strcmp(lsm->name, name) == 0) {
> > -				append_ordered_lsm(lsm, origin);
> > +			if (strcmp(lsm->name, name) == 0) {
> > +				if (lsm->order == LSM_ORDER_MUTABLE)
> > +					append_ordered_lsm(lsm, origin);
> >   				found = true;
> >   			}
> >   		}
> > @@ -306,6 +306,12 @@ static void __init ordered_lsm_parse(const char *order, const char *origin)
> >   		}
> >   	}
> >   
> > +	/* LSM_ORDER_LAST is always last. */
> > +	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
> > +		if (lsm->order == LSM_ORDER_LAST)
> > +			append_ordered_lsm(lsm, "   last");
> > +	}
> > +
> >   	/* Disable all LSMs not in the ordered list. */
> >   	for (lsm = __start_lsm_info; lsm < __end_lsm_info; lsm++) {
> >   		if (exists_ordered_lsm(lsm))