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Message-ID: <20200204234258.uwaqk3s3c42fxews@madcap2.tricolour.ca>
Date: Tue, 4 Feb 2020 18:42:58 -0500
From: Richard Guy Briggs <rgb@...hat.com>
To: Paul Moore <paul@...l-moore.com>
Cc: containers@...ts.linux-foundation.org, linux-api@...r.kernel.org,
Linux-Audit Mailing List <linux-audit@...hat.com>,
linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
sgrubb@...hat.com, omosnace@...hat.com, dhowells@...hat.com,
simo@...hat.com, Eric Paris <eparis@...isplace.org>,
Serge Hallyn <serge@...lyn.com>, ebiederm@...ssion.com,
nhorman@...driver.com, Dan Walsh <dwalsh@...hat.com>,
mpatel@...hat.com
Subject: Re: [PATCH ghak90 V8 11/16] audit: add support for containerid to
network namespaces
On 2020-01-22 16:28, Paul Moore wrote:
> On Tue, Dec 31, 2019 at 2:51 PM Richard Guy Briggs <rgb@...hat.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@...hat.com>
> > Acked-by: Neil Horman <nhorman@...driver.com>
> > Reviewed-by: Ondrej Mosnacek <omosnace@...hat.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)?
Ok, I've done this but at first I had doubts about the complexity.
> > + 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.
This was some of the complexity that concerned me, but switching to rcu
read locks helped. In this case, since a stale list would cause an
update issue and these counts aren't used or updated anywere else,
switching to an int makes sense.
> paul moore
- RGB
--
Richard Guy Briggs <rgb@...hat.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
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