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

Richard Guy Briggs
2018-12-27T15:33:54Z

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@redhat.com> 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@redhat.com>
> > > ---
> > > 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@redhat.com>
> 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@redhat.com
> https://www.redhat.com/mailman/listinfo/linux-audit

- RGB

--
Richard Guy Briggs <rgb@redhat.com>
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