Re: [PATCH ghak90 (was ghak32) V4 09/10] audit: NETFILTER_PKT: record each container ID associated with a netNS

[Richard Guy Briggs]

On 2018-10-31 15:30, Richard Guy Briggs wrote:
> On 2018-10-19 19:18, Paul Moore wrote:
> > On Sun, Aug 5, 2018 at 4:33 AM Richard Guy Briggs <rgb@xxxxxxxxxx> wrote:
> > > 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.
> > >
> > > Signed-off-by: Richard Guy Briggs <rgb@xxxxxxxxxx>
> > > ---
> > >  include/linux/audit.h    |  5 +++++
> > >  kernel/audit.c           | 26 ++++++++++++++++++++++++++
> > >  net/netfilter/xt_AUDIT.c | 12 ++++++++++--
> > >  3 files changed, 41 insertions(+), 2 deletions(-)
> > 
> > ...
> > 
> > > diff --git a/include/linux/audit.h b/include/linux/audit.h
> > > index 9a02095..8755f4d 100644
> > > --- a/include/linux/audit.h
> > > +++ b/include/linux/audit.h
> > > @@ -169,6 +169,8 @@ extern int audit_log_contid(struct audit_context *context,
> > >  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 int                 audit_update_lsm_rules(void);
> > >
> > > @@ -228,6 +230,9 @@ 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
> > >  #endif /* CONFIG_AUDIT */
> > > diff --git a/kernel/audit.c b/kernel/audit.c
> > > index c5fed3b..b23711c 100644
> > > --- a/kernel/audit.c
> > > +++ b/kernel/audit.c
> > > @@ -392,6 +392,32 @@ void audit_switch_task_namespaces(struct nsproxy *ns, struct task_struct *p)
> > >                 audit_netns_contid_add(new->net_ns, contid);
> > >  }
> > >
> > > +void audit_log_netns_contid_list(struct net *net, struct audit_context *context)
> > > +{
> > > +       spinlock_t *lock = audit_get_netns_contid_list_lock(net);
> > > +       struct audit_buffer *ab;
> > > +       struct audit_contid *cont;
> > > +       bool first = true;
> > > +
> > > +       /* Generate AUDIT_CONTAINER record with container ID CSV list */
> > > +       ab = audit_log_start(context, GFP_ATOMIC, AUDIT_CONTAINER);
> > > +       if (!ab) {
> > > +               audit_log_lost("out of memory in audit_log_netns_contid_list");
> > > +               return;
> > > +       }
> > > +       audit_log_format(ab, "contid=");
> > > +       spin_lock(lock);
> > > +       list_for_each_entry(cont, audit_get_netns_contid_list(net), list) {
> > > +               if (!first)
> > > +                       audit_log_format(ab, ",");
> > > +               audit_log_format(ab, "%llu", cont->id);
> > > +               first = false;
> > > +       }
> > > +       spin_unlock(lock);
> > 
> > This is looking like potentially a lot of work to be doing under a
> > spinlock, not to mention a single spinlock that is shared across CPUs.
> > Considering that I expect changes to the list to be somewhat
> > infrequent, this might be a good candidate for a RCU based locking
> > scheme.
> 
> Would something like this look reasonable?
> (This is on top of a patch to make contid list lock and unlock
> functions.)

Paul, could I please get your review on this locking approach I proposed
almost two months ago so I can be more reassured that it won't be an
issue in v5?  Thanks!

> diff --git a/include/linux/audit.h b/include/linux/audit.h
> index be5d6eb..9428fc3 100644
> --- a/include/linux/audit.h
> +++ b/include/linux/audit.h
> @@ -92,6 +92,7 @@ struct audit_contid {
>  	struct list_head	list;
>  	u64			id;
>  	refcount_t		refcount;
> +	struct rcu_head		rcu;
>  };
>  
>  extern int is_audit_feature_set(int which);
> diff --git a/kernel/audit.c b/kernel/audit.c
> index d5b58163..6f84c25 100644
> --- a/kernel/audit.c
> +++ b/kernel/audit.c
> @@ -106,7 +106,6 @@
>  struct audit_net {
>  	struct sock *sk;
>  	struct list_head contid_list;
> -	spinlock_t contid_list_lock;
>  };
>  
>  /**
> @@ -327,26 +326,6 @@ struct list_head *audit_get_netns_contid_list(const struct net *net)
>  	return &aunet->contid_list;
>  }
>  
> -static int audit_netns_contid_lock(const struct net *net)
> -{
> -	struct audit_net *aunet = net_generic(net, audit_net_id);
> -
> -	if (!aunet)
> -		return -EINVAL;
> -	spin_lock(aunet->contid_list_lock);
> -	return 0;
> -}
> -
> -static int audit_netns_contid_unlock(const struct net *net)
> -{
> -	struct audit_net *aunet = net_generic(net, audit_net_id);
> -
> -	if (!aunet)
> -		return -EINVAL;
> -	spin_unlock(aunet->contid_list_lock);
> -	return 0;
> -}
> -
>  void audit_netns_contid_add(struct net *net, u64 contid)
>  {
>  	struct list_head *contid_list = audit_get_netns_contid_list(net);
> @@ -354,10 +333,9 @@ void audit_netns_contid_add(struct net *net, u64 contid)
>  
>  	if (!audit_contid_valid(contid))
>  		return;
> -	if (audit_netns_contid_lock(net))
> -		return;
> +	rcu_read_lock();
>  	if (!list_empty(contid_list))
> -		list_for_each_entry(cont, contid_list, list)
> +		list_for_each_entry_rcu(cont, contid_list, list)
>  			if (cont->id == contid) {
>  				refcount_inc(&cont->refcount);
>  				goto out;
> @@ -367,10 +345,16 @@ void audit_netns_contid_add(struct net *net, u64 contid)
>  		INIT_LIST_HEAD(&cont->list);
>  		cont->id = contid;
>  		refcount_set(&cont->refcount, 1);
> -		list_add(&cont->list, contid_list);
> +		list_add_rcu(&cont->list, contid_list);
>  	}
>  out:
> -	audit_netns_contid_unlock(net);
> +	rcu_read_unlock();
> +}
> +
> +audit_free_contid_rcu(struct rcu_head *head) {
> +	struct audit_contid *contid = container_of(head, struct audit_contid, rcu);
> +
> +	kfree(contid);
>  }
>  
>  void audit_netns_contid_del(struct net *net, u64 contid)
> @@ -380,17 +364,16 @@ void audit_netns_contid_del(struct net *net, u64 contid)
>  
>  	if (!audit_contid_valid(contid))
>  		return;
> -	if (audit_netns_contid_lock(net))
> -		return;
> +	rcu_read_lock();
>  	if (!list_empty(contid_list))
> -		list_for_each_entry(cont, contid_list, list)
> +		list_for_each_entry_rcu(cont, contid_list, list)
>  			if (cont->id == contid) {
> -				list_del(&cont->list);
> +				list_del_rcu(&cont->list);
>  				if (refcount_dec_and_test(&cont->refcount))
> -					kfree(cont);
> +					call_rcu(&cont->rcu, audit_free_contid_rcu);
>  				break;
>  			}
> -	audit_netns_contid_unlock(net);
> +	rcu_read_unlock();
>  }
>  
>  void audit_switch_task_namespaces(struct nsproxy *ns, struct task_struct *p)
> @@ -418,15 +401,14 @@ void audit_log_netns_contid_list(struct net *net, struct audit_context *context)
>  		return;
>  	}
>  	audit_log_format(ab, "ref=net contid=");
> -	if (audit_netns_contid_lock(net))
> -		return;
> -	list_for_each_entry(cont, audit_get_netns_contid_list(net), list) {
> +	rcu_read_lock();
> +	list_for_each_entry_rcu(cont, audit_get_netns_contid_list(net), list) {
>  		if (!first)
>  			audit_log_format(ab, ",");
>  		audit_log_format(ab, "%llu", cont->id);
>  		first = false;
>  	}
> -	audit_netns_contid_unlock(net);
> +	rcu_read_unlock();
>  	audit_log_end(ab);
>  }
>  EXPORT_SYMBOL(audit_log_netns_contid_list);
> @@ -1674,7 +1656,6 @@ static int __net_init audit_net_init(struct net *net)
>  		.flags	= NL_CFG_F_NONROOT_RECV,
>  		.groups	= AUDIT_NLGRP_MAX,
>  	};
> -
>  	struct audit_net *aunet = net_generic(net, audit_net_id);
>  
>  	aunet->sk = netlink_kernel_create(net, NETLINK_AUDIT, &cfg);
> @@ -1684,8 +1665,6 @@ static int __net_init audit_net_init(struct net *net)
>  	}
>  	aunet->sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
>  	INIT_LIST_HEAD(&aunet->contid_list);
> -	spin_lock_init(&aunet->contid_list_lock);
> -
>  	return 0;
>  }
>  
> > 
> > > +       audit_log_end(ab);
> > > +}
> > > +EXPORT_SYMBOL(audit_log_netns_contid_list);
> > >
> > >  void audit_panic(const char *message)
> > >  {
> > >         switch (audit_failure) {
> > > diff --git a/net/netfilter/xt_AUDIT.c b/net/netfilter/xt_AUDIT.c
> > > index af883f1..44fac3f 100644
> > > --- a/net/netfilter/xt_AUDIT.c
> > > +++ b/net/netfilter/xt_AUDIT.c
> > > @@ -71,10 +71,13 @@ static bool audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)
> > >  {
> > >         struct audit_buffer *ab;
> > >         int fam = -1;
> > > +       struct audit_context *context;
> > > +       struct net *net;
> > >
> > >         if (audit_enabled == AUDIT_OFF)
> > > -               goto errout;
> > > -       ab = audit_log_start(NULL, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
> > > +               goto out;
> > > +       context = audit_alloc_local(GFP_ATOMIC);
> > > +       ab = audit_log_start(context, GFP_ATOMIC, AUDIT_NETFILTER_PKT);
> > >         if (ab == NULL)
> > >                 goto errout;
> > >
> > > @@ -104,7 +107,12 @@ static bool audit_ip6(struct audit_buffer *ab, struct sk_buff *skb)
> > >
> > >         audit_log_end(ab);
> > >
> > > +       net = xt_net(par);
> > > +       audit_log_netns_contid_list(net, context);
> > > +
> > >  errout:
> > > +       audit_free_context(context);
> > > +out:
> > >         return XT_CONTINUE;
> > >  }
> > >
> > 
> > --
> > paul moore
> > www.paul-moore.com
> 
> - RGB
> 
> --
> Richard Guy Briggs <rgb@xxxxxxxxxx>
> Sr. S/W Engineer, Kernel Security, Base Operating Systems
> Remote, Ottawa, Red Hat Canada
> IRC: rgb, SunRaycer
> Voice: +1.647.777.2635, Internal: (81) 32635
> 
> --
> Linux-audit mailing list
> Linux-audit@xxxxxxxxxx
> https://www.redhat.com/mailman/listinfo/linux-audit

- RGB

--
Richard Guy Briggs <rgb@xxxxxxxxxx>
Sr. S/W Engineer, Kernel Security, Base Operating Systems
Remote, Ottawa, Red Hat Canada
IRC: rgb, SunRaycer
Voice: +1.647.777.2635, Internal: (81) 32635