linux-kernel - Re: [PATCH v3 4/5] LSM: lsm_context in security_dentry_init

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Message-ID: <CAHC9VhSSpLx=ku7ZJ7qVxHHyOZZPQWs_hoxVRZpTfhOJ=T2X9w@mail.gmail.com>
Date: Thu, 20 Feb 2025 12:40:45 -0500
From: Paul Moore <paul@...l-moore.com>
To: Stephen Smalley <stephen.smalley.work@...il.com>
Cc: Casey Schaufler <casey@...aufler-ca.com>, linux-security-module@...r.kernel.org, 
	jmorris@...ei.org, serge@...lyn.com, keescook@...omium.org, 
	john.johansen@...onical.com, penguin-kernel@...ove.sakura.ne.jp, 
	linux-kernel@...r.kernel.org, selinux@...r.kernel.org, mic@...ikod.net, 
	ceph-devel@...r.kernel.org, linux-nfs@...r.kernel.org
Subject: Re: [PATCH v3 4/5] LSM: lsm_context in security_dentry_init_security

On Thu, Feb 20, 2025 at 11:43 AM Stephen Smalley
<stephen.smalley.work@...il.com> wrote:
> On Wed, Oct 23, 2024 at 5:23 PM Casey Schaufler <casey@...aufler-ca.com> wrote:
> >
> > Replace the (secctx,seclen) pointer pair with a single lsm_context
> > pointer to allow return of the LSM identifier along with the context
> > and context length. This allows security_release_secctx() to know how
> > to release the context. Callers have been modified to use or save the
> > returned data from the new structure.
> >
> > Signed-off-by: Casey Schaufler <casey@...aufler-ca.com>
> > Cc: ceph-devel@...r.kernel.org
> > Cc: linux-nfs@...r.kernel.org
> > ---
> >  fs/ceph/super.h               |  3 +--
> >  fs/ceph/xattr.c               | 16 ++++++----------
> >  fs/fuse/dir.c                 | 35 ++++++++++++++++++-----------------
> >  fs/nfs/nfs4proc.c             | 20 ++++++++++++--------
> >  include/linux/lsm_hook_defs.h |  2 +-
> >  include/linux/security.h      | 26 +++-----------------------
> >  security/security.c           |  9 ++++-----
> >  security/selinux/hooks.c      |  9 +++++----
> >  8 files changed, 50 insertions(+), 70 deletions(-)
> >
>
> > diff --git a/fs/nfs/nfs4proc.c b/fs/nfs/nfs4proc.c
> > index 76776d716744..0b116ef3a752 100644
> > --- a/fs/nfs/nfs4proc.c
> > +++ b/fs/nfs/nfs4proc.c
> > @@ -114,6 +114,7 @@ static inline struct nfs4_label *
> >  nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
> >         struct iattr *sattr, struct nfs4_label *label)
> >  {
> > +       struct lsm_context shim;
> >         int err;
> >
> >         if (label == NULL)
> > @@ -128,21 +129,24 @@ nfs4_label_init_security(struct inode *dir, struct dentry *dentry,
> >         label->label = NULL;
> >
> >         err = security_dentry_init_security(dentry, sattr->ia_mode,
> > -                               &dentry->d_name, NULL,
> > -                               (void **)&label->label, &label->len);
> > -       if (err == 0)
> > -               return label;
> > +                               &dentry->d_name, NULL, &shim);
> > +       if (err)
> > +               return NULL;
> >
> > -       return NULL;
> > +       label->label = shim.context;
> > +       label->len = shim.len;
> > +       return label;
> >  }
> >  static inline void
> >  nfs4_label_release_security(struct nfs4_label *label)
> >  {
> > -       struct lsm_context scaff; /* scaffolding */
> > +       struct lsm_context shim;
> >
> >         if (label) {
> > -               lsmcontext_init(&scaff, label->label, label->len, 0);
> > -               security_release_secctx(&scaff);
> > +               shim.context = label->label;
> > +               shim.len = label->len;
> > +               shim.id = LSM_ID_UNDEF;
>
> Is there a patch that follows this one to fix this? Otherwise, setting
> this to UNDEF causes SELinux to NOT free the context, which produces a
> memory leak for every NFS inode security context. Reported by kmemleak
> when running the selinux-testsuite NFS tests.

I don't recall seeing anything related to this, but patches are
definitely welcome.

-- 
paul-moore.com