Re: [PATCH v6 02/17] ima: Define ns_status for storing namespaced iint data

[Stefan Berger]

On 12/15/21 16:12, Mimi Zohar wrote:
> Hi Stefan,
>
> On Fri, 2021-12-10 at 14:47 -0500, Stefan Berger wrote:
> > From: Mehmet Kayaalp <mkayaalp@xxxxxxxxxxxxxxxxxx>
> >
> > This patch adds an rbtree to the IMA namespace structure that stores a
> > namespaced version of iint->flags in ns_status struct. Similar to the
> > integrity_iint_cache, both the iint ns_struct are looked up using the
> > inode pointer value. The lookup, allocate, and insertion code is also
> > similar, except ns_struct is not free'd when the inode is free'd.
> > Instead, the lookup verifies the i_ino and i_generation fields are also a
> > match.
> >
> > Signed-off-by: Mehmet Kayaalp <mkayaalp@xxxxxxxxxxxxxxxxxx>
> > Signed-off-by: Stefan Berger <stefanb@xxxxxxxxxxxxx>
> Again, hopefully it isn't premature for generic comments:
>
> - Function/inline comments would be appreciated, especially when the
> code differs from the original code.  Example below.
>
> > diff --git a/security/integrity/ima/ima_init_ima_ns.c b/security/integrity/ima/ima_init_ima_ns.c
> > index f820686baf9f..08781a44f7bf 100644
> > --- a/security/integrity/ima/ima_init_ima_ns.c
> > +++ b/security/integrity/ima/ima_init_ima_ns.c
> > @@ -14,11 +14,18 @@
> >   #include <linux/user_namespace.h>
> >   #include <linux/ima.h>
> >   #include <linux/proc_ns.h>
> > +#include <linux/slab.h>
> >   
> >   #include "ima.h"
> >   
> >   int ima_init_namespace(struct ima_namespace *ns)
> >   {
> > +	ns->ns_status_tree = RB_ROOT;
> > +	rwlock_init(&ns->ns_status_lock);
> > +	ns->ns_status_cache = KMEM_CACHE(ns_status, SLAB_PANIC);
> > +	if (!ns->ns_status_cache)
> > +		return -ENOMEM;
> > +
> For example, using KMEM_CACHE() is probably correct here, at least for
> now, but it is different than the original code which uses
> kmem_cache_alloc() with init_once().  Memory cleanup is done on free,
> before it is re-used.

KMEM_CACHE + kmem_cache_alloc/zalloc() are pretty common. What kind of 
comment would be helpful here?

   Stefan

> thanks,
>
> Mimi
>
> >   	return 0;
> >   }