linux-kernel - Re: [PATCH v2] selinux: log anon inode class name

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Date:   Mon, 2 May 2022 15:39:41 +0200
From:   Christian Göttsche <cgzones@...glemail.com>
To:     Paul Moore <paul@...l-moore.com>
Cc:     SElinux list <selinux@...r.kernel.org>,
        James Morris <jmorris@...ei.org>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        Stephen Smalley <stephen.smalley.work@...il.com>,
        Eric Paris <eparis@...isplace.org>,
        Richard Guy Briggs <rgb@...hat.com>,
        Ondrej Mosnacek <omosnace@...hat.com>,
        Linux kernel mailing list <linux-kernel@...r.kernel.org>,
        linux-security-module@...r.kernel.org
Subject: Re: [PATCH v2] selinux: log anon inode class name

On Wed, 27 Apr 2022 at 15:19, Paul Moore <paul@...l-moore.com> wrote:
>
> On Mon, Apr 4, 2022 at 4:18 PM Paul Moore <paul@...l-moore.com> wrote:
> > On Tue, Mar 8, 2022 at 12:09 PM Christian Göttsche
> > <cgzones@...glemail.com> wrote:
> > >
> > > Log the anonymous inode class name in the security hook
> > > inode_init_security_anon.  This name is the key for name based type
> > > transitions on the anon_inode security class on creation.  Example:
> > >
> > >     type=AVC msg=audit(02/16/22 22:02:50.585:216) : avc:  granted \
> > >         { create } for  pid=2136 comm=mariadbd anonclass="[io_uring]" \
> > >         scontext=system_u:system_r:mysqld_t:s0 \
> > >         tcontext=system_u:system_r:mysqld_iouring_t:s0 tclass=anon_inode
> > >
> > > Add a new LSM audit data type holding the inode and the class name.
> > >
> > > Signed-off-by: Christian Göttsche <cgzones@...glemail.com>
> > >
> > > ---
> > > v2:
> > >   - drop dev= and name= output for anonymous inodes, and hence simplify
> > >     the common_audit_data union member.
> > >   - drop WARN_ON() on empty name passed to inode_init_security_anon hook
> > > ---
> > >  include/linux/lsm_audit.h | 2 ++
> > >  security/lsm_audit.c      | 4 ++++
> > >  security/selinux/hooks.c  | 4 ++--
> > >  3 files changed, 8 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/include/linux/lsm_audit.h b/include/linux/lsm_audit.h
> > > index 17d02eda9538..97a8b21eb033 100644
> > > --- a/include/linux/lsm_audit.h
> > > +++ b/include/linux/lsm_audit.h
> > > @@ -76,6 +76,7 @@ struct common_audit_data {
> > >  #define LSM_AUDIT_DATA_IBENDPORT 14
> > >  #define LSM_AUDIT_DATA_LOCKDOWN 15
> > >  #define LSM_AUDIT_DATA_NOTIFICATION 16
> > > +#define LSM_AUDIT_DATA_ANONINODE       17
> > >         union   {
> > >                 struct path path;
> > >                 struct dentry *dentry;
> > > @@ -96,6 +97,7 @@ struct common_audit_data {
> > >                 struct lsm_ibpkey_audit *ibpkey;
> > >                 struct lsm_ibendport_audit *ibendport;
> > >                 int reason;
> > > +               const char *anonclass;
> > >         } u;
> > >         /* this union contains LSM specific data */
> > >         union {
> > > diff --git a/security/lsm_audit.c b/security/lsm_audit.c
> > > index 1897cbf6fc69..981f6a4e4590 100644
> > > --- a/security/lsm_audit.c
> > > +++ b/security/lsm_audit.c
> > > @@ -433,6 +433,10 @@ static void dump_common_audit_data(struct audit_buffer *ab,
> > >                 audit_log_format(ab, " lockdown_reason=\"%s\"",
> > >                                  lockdown_reasons[a->u.reason]);
> > >                 break;
> > > +       case LSM_AUDIT_DATA_ANONINODE:
> > > +               audit_log_format(ab, " anonclass=");
> > > +               audit_log_untrustedstring(ab, a->u.anonclass);
> >
> > My apologies, I didn't notice this in the previous patch ... I don't
> > think we need to log this as an untrusted string as the string value
> > is coming from the kernel, not userspace, so we could rewrite the
> > above as the following:
> >
> >   audit_log_format(ab, " anonclass=%s", a->u.anonclass);
> >
> > ... if you are okay with that, I can make the change when I merge the
> > patch or you can submit another revision, let me know which you would
> > prefer.

Feel free to adjust while merging, thanks.

> >
> > The rest of the patch looks good, thanks!
>
> Hi Christian,
>
> I just wanted to follow up on this as we are at -rc4 this week and if
> we want this to go during the next merge window this would need to be
> merged soon ...
>
> --
> paul-moore.com