linux-kernel - Re: [PATCH v5 13/23] security: Introduce file_pre_free

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Message-ID: <CAHC9VhR29VEybYHsx65E=-YYNLuLHOVm6BF2H==bEcrcHU7Ksg@mail.gmail.com>
Date:   Thu, 16 Nov 2023 13:41:47 -0500
From:   Paul Moore <paul@...l-moore.com>
To:     Roberto Sassu <roberto.sassu@...weicloud.com>
Cc:     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,
        jmorris@...ei.org, serge@...lyn.com, zohar@...ux.ibm.com,
        dmitry.kasatkin@...il.com, dhowells@...hat.com, jarkko@...nel.org,
        stephen.smalley.work@...il.com, eparis@...isplace.org,
        casey@...aufler-ca.com, mic@...ikod.net,
        linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-nfs@...r.kernel.org, linux-security-module@...r.kernel.org,
        linux-integrity@...r.kernel.org, keyrings@...r.kernel.org,
        selinux@...r.kernel.org, Roberto Sassu <roberto.sassu@...wei.com>
Subject: Re: [PATCH v5 13/23] security: Introduce file_pre_free_security hook

On Thu, Nov 16, 2023 at 4:47 AM Roberto Sassu
<roberto.sassu@...weicloud.com> wrote:
> On Wed, 2023-11-15 at 23:33 -0500, Paul Moore wrote:
> > On Nov  7, 2023 Roberto Sassu <roberto.sassu@...weicloud.com> wrote:
> > >
> > > In preparation for moving IMA and EVM to the LSM infrastructure, introduce
> > > the file_pre_free_security hook.
> > >
> > > IMA calculates at file close the new digest of the file content and writes
> > > it to security.ima, so that appraisal at next file access succeeds.
> > >
> > > LSMs could also take some action before the last reference of a file is
> > > released.
> > >
> > > The new hook cannot return an error and cannot cause the operation to be
> > > reverted.
> > >
> > > Signed-off-by: Roberto Sassu <roberto.sassu@...wei.com>
> > > Acked-by: Casey Schaufler <casey@...aufler-ca.com>
> > > Reviewed-by: Mimi Zohar <zohar@...ux.ibm.com>
> > > ---
> > >  fs/file_table.c               |  1 +
> > >  include/linux/lsm_hook_defs.h |  1 +
> > >  include/linux/security.h      |  4 ++++
> > >  security/security.c           | 11 +++++++++++
> > >  4 files changed, 17 insertions(+)
> > >
> > > diff --git a/fs/file_table.c b/fs/file_table.c
> > > index de4a2915bfd4..64ed74555e64 100644
> > > --- a/fs/file_table.c
> > > +++ b/fs/file_table.c
> > > @@ -385,6 +385,7 @@ static void __fput(struct file *file)
> > >     eventpoll_release(file);
> > >     locks_remove_file(file);
> > >
> > > +   security_file_pre_free(file);
> >
> > I worry that security_file_pre_free() is a misleading name as "free"
> > tends to imply memory management tasks, which isn't the main focus of
> > this hook.  What do you think of security_file_release() or
> > security_file_put() instead?
>
> security_file_release() would be fine for me.

Okay, assuming no objections for anyone else let's go with that.
Thanks for indulging my naming nitpick :)

-- 
paul-moore.com