linux-kernel - Re: [PATCH v3 02/25] ima: Align ima_post_path_mknod() definition with LSM infrastructure

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Date:   Thu, 12 Oct 2023 13:10:50 -0400
From:   Mimi Zohar <zohar@...ux.ibm.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>,
        viro@...iv.linux.org.uk, brauner@...nel.org,
        chuck.lever@...cle.com, jlayton@...nel.org, neilb@...e.de,
        kolga@...app.com, Dai.Ngo@...cle.com, tom@...pey.com,
        dmitry.kasatkin@...il.com, paul@...l-moore.com, jmorris@...ei.org,
        serge@...lyn.com, dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        casey@...aufler-ca.com
Cc:     linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-integrity@...r.kernel.org,
        linux-security-module@...r.kernel.org, keyrings@...r.kernel.org,
        selinux@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v3 02/25] ima: Align ima_post_path_mknod() definition
 with LSM infrastructure

> > > > > We need to make sure that ima_post_path_mknod() has the same parameters
> > > > > as the LSM hook at the time we register it to the LSM infrastructure.
> > > > 
> > > > I'm trying to understand why the pre hook parameters and the missing
> > > > IMA parameter are used, as opposed to just defining the new
> > > > post_path_mknod hook like IMA.
> > > 
> > > As an empyrical rule, I pass the same parameters as the corresponding
> > > pre hook (plus idmap, in this case). This is similar to the
> > > inode_setxattr hook. But I can be wrong, if desired I can reduce.
> > 
> > The inode_setxattr hook change example is legitimate, as EVM includes
> > idmap, while IMA doesn't. 
> > 
> > Unless there is a good reason for the additional parameters, I'm not
> > sure that adding them makes sense.  Not modifying the parameter list
> > will reduce the size of this patch set.
> 
> The hook is going to be used by any LSM. Without knowing all the
> possible use cases, maybe it is better to include more information now,
> than modifying the hook and respective implementations later.
> 
> (again, no problem to reduce)

Unless there is a known use case for a specific parameter, please
minimize them.   Additional parameters can be added later as needed. 

-- 
thanks,

Mimi