Re: [PATCH ghak90 V8 11/16] audit: add support for containerid to network namespaces

[Paul Moore <paul@paul-moore.com>]

On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs <rgb@redhat.com> wrote:
>
> This also adds support to qualify NETFILTER_PKT records.
>
> Audit events could happen in a network namespace outside of a task
> context due to packets received from the net that trigger an auditing
> rule prior to being associated with a running task.  The network
> namespace could be in use by multiple containers by association to the
> tasks in that network namespace.  We still want a way to attribute
> these events to any potential containers.  Keep a list per network
> namespace to track these audit container identifiiers.
>
> Add/increment the audit container identifier on:
> - initial setting of the audit container identifier via /proc
> - clone/fork call that inherits an audit container identifier
> - unshare call that inherits an audit container identifier
> - setns call that inherits an audit container identifier
> Delete/decrement the audit container identifier on:
> - an inherited audit container identifier dropped when child set
> - process exit
> - unshare call that drops a net namespace
> - setns call that drops a net namespace
>
> Add audit container identifier auxiliary record(s) to NETFILTER_PKT
> event standalone records.  Iterate through all potential audit container
> identifiers associated with a network namespace.
>
> Please see the github audit kernel issue for contid net support:
>   https://github.com/linux-audit/audit-kernel/issues/92
> Please see the github audit testsuiite issue for the test case:
>   https://github.com/linux-audit/audit-testsuite/issues/64
> Please see the github audit wiki for the feature overview:
>   https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID
> Signed-off-by: Richard Guy Briggs <rgb@redhat.com>
> Acked-by: Neil Horman <nhorman@tuxdriver.com>
> Reviewed-by: Ondrej Mosnacek <omosnace@redhat.com>
> ---
>  include/linux/audit.h    |  24 +++++++++
>  kernel/audit.c           | 132 ++++++++++++++++++++++++++++++++++++++++++++++-
>  kernel/nsproxy.c         |   4 ++
>  net/netfilter/nft_log.c  |  11 +++-
>  net/netfilter/xt_AUDIT.c |  11 +++-
>  5 files changed, 176 insertions(+), 6 deletions(-)

...

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index 5531d37a4226..ed8d5b74758d 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -12,6 +12,7 @@
>  #include <linux/sched.h>
>  #include <linux/ptrace.h>
>  #include <uapi/linux/audit.h>
> +#include <linux/refcount.h>
>
>  #define AUDIT_INO_UNSET ((unsigned long)-1)
>  #define AUDIT_DEV_UNSET ((dev_t)-1)
> @@ -121,6 +122,13 @@ struct audit_task_info {
>
>  extern struct audit_task_info init_struct_audit;
>
> +struct audit_contobj_netns {
> +       struct list_head        list;
> +       u64                     id;

Since we now track audit container IDs in their own structure, why not
link directly to the audit container ID object (and bump the
refcount)?

> +       refcount_t              refcount;
> +       struct rcu_head         rcu;
> +};
> +
>  extern int is_audit_feature_set(int which);
>
>  extern int __init audit_register_class(int class, unsigned *list);
> @@ -225,6 +233,12 @@ static inline u64 audit_get_contid(struct task_struct *tsk)
>  }
>
>  extern void audit_log_container_id(struct audit_context *context, u64 contid);
> +extern void audit_netns_contid_add(struct net *net, u64 contid);
> +extern void audit_netns_contid_del(struct net *net, u64 contid);
> +extern void audit_switch_task_namespaces(struct nsproxy *ns,
> +                                        struct task_struct *p);
> +extern void audit_log_netns_contid_list(struct net *net,
> +                                       struct audit_context *context);
>
>  extern u32 audit_enabled;
>
> @@ -297,6 +311,16 @@ static inline u64 audit_get_contid(struct task_struct *tsk)
>
>  static inline void audit_log_container_id(struct audit_context *context, u64 contid)
>  { }
> +static inline void audit_netns_contid_add(struct net *net, u64 contid)
> +{ }
> +static inline void audit_netns_contid_del(struct net *net, u64 contid)
> +{ }
> +static inline void audit_switch_task_namespaces(struct nsproxy *ns,
> +                                               struct task_struct *p)
> +{ }
> +static inline void audit_log_netns_contid_list(struct net *net,
> +                                              struct audit_context *context)
> +{ }
>
>  #define audit_enabled AUDIT_OFF
>
> diff --git a/kernel/audit.c b/kernel/audit.c
> index d4e6eafe5644..f7a8d3288ca0 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -59,6 +59,7 @@
>  #include <linux/freezer.h>
>  #include <linux/pid_namespace.h>
>  #include <net/netns/generic.h>
> +#include <net/net_namespace.h>
>
>  #include "audit.h"
>
> @@ -86,9 +87,13 @@
>  /**
>   * struct audit_net - audit private network namespace data
>   * @sk: communication socket
> + * @contid_list: audit container identifier list
> + * @contid_list_lock audit container identifier list lock
>   */
>  struct audit_net {
>         struct sock *sk;
> +       struct list_head contid_list;
> +       spinlock_t contid_list_lock;
>  };
>
>  /**
> @@ -305,8 +310,11 @@ struct audit_task_info init_struct_audit = {
>  void audit_free(struct task_struct *tsk)
>  {
>         struct audit_task_info *info = tsk->audit;
> +       struct nsproxy *ns = tsk->nsproxy;
>
>         audit_free_syscall(tsk);
> +       if (ns)
> +               audit_netns_contid_del(ns->net_ns, audit_get_contid(tsk));
>         /* Freeing the audit_task_info struct must be performed after
>          * audit_log_exit() due to need for loginuid and sessionid.
>          */
> @@ -409,6 +417,120 @@ static struct sock *audit_get_sk(const struct net *net)
>         return aunet->sk;
>  }
>
> +void audit_netns_contid_add(struct net *net, u64 contid)
> +{
> +       struct audit_net *aunet;
> +       struct list_head *contid_list;
> +       struct audit_contobj_netns *cont;
> +
> +       if (!net)
> +               return;
> +       if (!audit_contid_valid(contid))
> +               return;
> +       aunet = net_generic(net, audit_net_id);
> +       if (!aunet)
> +               return;
> +       contid_list = &aunet->contid_list;
> +       rcu_read_lock();
> +       list_for_each_entry_rcu(cont, contid_list, list)
> +               if (cont->id == contid) {
> +                       spin_lock(&aunet->contid_list_lock);
> +                       refcount_inc(&cont->refcount);
> +                       spin_unlock(&aunet->contid_list_lock);
> +                       goto out;
> +               }
> +       cont = kmalloc(sizeof(*cont), GFP_ATOMIC);
> +       if (cont) {
> +               INIT_LIST_HEAD(&cont->list);
> +               cont->id = contid;
> +               refcount_set(&cont->refcount, 1);
> +               spin_lock(&aunet->contid_list_lock);
> +               list_add_rcu(&cont->list, contid_list);
> +               spin_unlock(&aunet->contid_list_lock);
> +       }
> +out:
> +       rcu_read_unlock();
> +}

See my comments about refcount_t, spinlocks, and list manipulation
races from earlier in the patchset; the same thing applies to the
function above.


--
paul moore
www.paul-moore.com