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

Richard Guy Briggs
2018-10-31T19:30:18Z

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.)

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