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    SubjectRe: [PATCH 1/3] selinux: Implement LSM notification system
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    On Wed, 2017-04-26 at 08:38 -0700, Casey Schaufler wrote:
    > On 4/26/2017 8:02 AM, Sebastien Buisson wrote:
    > > From: Daniel Jurgens <danielj@mellanox.com>
    > >
    > > Add a generic notification mechanism in the LSM. Interested
    > > consumers
    > > can register a callback with the LSM and security modules can
    > > produce
    > > events.
    >
    > Why is this a generic mechanism? Do you ever see anyone
    > other than SELinux using it?

    I do - any security module that wants to support access control over
    Lustre filesystems or Infiniband. Seems ironic for you to be arguing
    for a SELinux-specific interface rather than a LSM interface.

    >
    > > Add a call to the notification mechanism from SELinux when the AVC
    > > cache changes.
    >
    > This seems like a whole lot of mechanism for
    > something you could accomplish with a log message.
    > What am I missing?

    It's a notification to a kernel subsystem that policy has changed so
    that the subsystem can update any cached state.

    >
    > >
    > > Signed-off-by: Daniel Jurgens <danielj@mellanox.com>
    > > Signed-off-by: Sebastien Buisson <sbuisson@ddn.com>
    > > ---
    > >  include/linux/security.h | 23 +++++++++++++++++++++++
    > >  security/security.c      | 20 ++++++++++++++++++++
    > >  security/selinux/hooks.c | 12 ++++++++++++
    > >  3 files changed, 55 insertions(+)
    > >
    > > diff --git a/include/linux/security.h b/include/linux/security.h
    > > index af675b5..73a9c93 100644
    > > --- a/include/linux/security.h
    > > +++ b/include/linux/security.h
    > > @@ -68,6 +68,10 @@
    > >  struct user_namespace;
    > >  struct timezone;
    > >  
    > > +enum lsm_event {
    > > + LSM_POLICY_CHANGE,
    > > +};
    > > +
    > >  /* These functions are in security/commoncap.c */
    > >  extern int cap_capable(const struct cred *cred, struct
    > > user_namespace *ns,
    > >          int cap, int audit);
    > > @@ -163,6 +167,10 @@ struct security_mnt_opts {
    > >   int num_mnt_opts;
    > >  };
    > >  
    > > +int call_lsm_notifier(enum lsm_event event, void *data);
    > > +int register_lsm_notifier(struct notifier_block *nb);
    > > +int unregister_lsm_notifier(struct notifier_block *nb);
    > > +
    > >  static inline void security_init_mnt_opts(struct security_mnt_opts
    > > *opts)
    > >  {
    > >   opts->mnt_opts = NULL;
    > > @@ -381,6 +389,21 @@ int security_sem_semop(struct sem_array *sma,
    > > struct sembuf *sops,
    > >  struct security_mnt_opts {
    > >  };
    > >  
    > > +static inline int call_lsm_notifier(enum lsm_event event, void
    > > *data)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static inline int register_lsm_notifier(struct notifier_block *nb)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > > +static inline  int unregister_lsm_notifier(struct notifier_block
    > > *nb)
    > > +{
    > > + return 0;
    > > +}
    > > +
    > >  static inline void security_init_mnt_opts(struct security_mnt_opts
    > > *opts)
    > >  {
    > >  }
    > > diff --git a/security/security.c b/security/security.c
    > > index b9fea39..ef9d9e1 100644
    > > --- a/security/security.c
    > > +++ b/security/security.c
    > > @@ -32,6 +32,8 @@
    > >  /* Maximum number of letters for an LSM name string */
    > >  #define SECURITY_NAME_MAX 10
    > >  
    > > +static ATOMIC_NOTIFIER_HEAD(lsm_notifier_chain);
    > > +
    > >  struct security_hook_heads security_hook_heads
    > > __lsm_ro_after_init;
    > >  char *lsm_names;
    > >  /* Boot-time LSM user choice */
    > > @@ -146,6 +148,24 @@ void __init security_add_hooks(struct
    > > security_hook_list *hooks, int count,
    > >   panic("%s - Cannot get early memory.\n",
    > > __func__);
    > >  }
    > >  
    > > +int call_lsm_notifier(enum lsm_event event, void *data)
    > > +{
    > > + return atomic_notifier_call_chain(&lsm_notifier_chain,
    > > event, data);
    > > +}
    > > +EXPORT_SYMBOL(call_lsm_notifier);
    > > +
    > > +int register_lsm_notifier(struct notifier_block *nb)
    > > +{
    > > + return atomic_notifier_chain_register(&lsm_notifier_chain,
    > > nb);
    > > +}
    > > +EXPORT_SYMBOL(register_lsm_notifier);
    > > +
    > > +int unregister_lsm_notifier(struct notifier_block *nb)
    > > +{
    > > + return
    > > atomic_notifier_chain_unregister(&lsm_notifier_chain, nb);
    > > +}
    > > +EXPORT_SYMBOL(unregister_lsm_notifier);
    > > +
    > >  /*
    > >   * Hook list operation macros.
    > >   *
    > > diff --git a/security/selinux/hooks.c b/security/selinux/hooks.c
    > > index e67a526..a4d36f8 100644
    > > --- a/security/selinux/hooks.c
    > > +++ b/security/selinux/hooks.c
    > > @@ -171,6 +171,14 @@ static int selinux_netcache_avc_callback(u32
    > > event)
    > >   return 0;
    > >  }
    > >  
    > > +static int selinux_lsm_notifier_avc_callback(u32 event)
    > > +{
    > > + if (event == AVC_CALLBACK_RESET)
    > > + call_lsm_notifier(LSM_POLICY_CHANGE, NULL);
    > > +
    > > + return 0;
    > > +}
    > > +
    > >  /*
    > >   * initialise the security for the init task
    > >   */
    > > @@ -6379,6 +6387,10 @@ static __init int selinux_init(void)
    > >   if (avc_add_callback(selinux_netcache_avc_callback,
    > > AVC_CALLBACK_RESET))
    > >   panic("SELinux: Unable to register AVC netcache
    > > callback\n");
    > >  
    > > + if (avc_add_callback(selinux_lsm_notifier_avc_callback,
    > > +      AVC_CALLBACK_RESET))
    > > + panic("SELinux: Unable to register AVC LSM
    > > notifier callback\n");
    > > +
    > >   if (selinux_enforcing)
    > >   printk(KERN_DEBUG "SELinux:  Starting in enforcing
    > > mode\n");
    > >   else

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