Re: [PATCH ghak90 V5 09/10] audit: add support for containerid to network namespaces

On 2019-03-27 23:42, Ondrej Mosnacek wrote: > On Fri, Mar 15, 2019 at 7:35 PM Richard Guy Briggs <rgb(a)redhat.com&gt; wrote: > > 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 > > > > See: https://github.com/linux-audit/audit-kernel/issues/92 > > See: https://github.com/linux-audit/audit-testsuite/issues/64 > > See: https://github.com/linux-audit/audit-kernel/wiki/RFE-Audit-Container-ID > > Signed-off-by: Richard Guy Briggs <rgb(a)redhat.com&gt; > > --- > > include/linux/audit.h | 19 ++++++++++++ > > kernel/audit.c | 86 +++++++++++++++++++++++++++++++++++++++++++++++++-- > > kernel/nsproxy.c | 4 +++ > > 3 files changed, 106 insertions(+), 3 deletions(-) > > > > diff --git a/include/linux/audit.h b/include/linux/audit.h > > index fa19fa408931..70255c2dfb9f 100644 > > --- a/include/linux/audit.h > > +++ b/include/linux/audit.h > > @@ -27,6 +27,7 @@ > > #include <linux/ptrace.h> > > #include <linux/namei.h> /* LOOKUP_* */ > > #include <uapi/linux/audit.h> > > +#include <linux/refcount.h> > > > > #define AUDIT_INO_UNSET ((unsigned long)-1) > > #define AUDIT_DEV_UNSET ((dev_t)-1) > > @@ -99,6 +100,13 @@ struct audit_task_info { > > > > extern struct audit_task_info init_struct_audit; > > > > +struct audit_contid { > > + struct list_head list; > > + u64 id; > > + refcount_t refcount; > > Hm, since we only ever touch the refcount under a spinlock, I wonder > if we could just make it a regular unsigned int (we don't need the > atomicity guarantees). OTOH, refcount_t comes with some extra overflow > checking, so it's probably better to leave it as is... Since the update is done using rcu-safe methods, do we even need the spin_lock? Neil? Paul? > > + struct rcu_head rcu; > > +}; > > + > > extern int is_audit_feature_set(int which); > > > > extern int __init audit_register_class(int class, unsigned *list); > > @@ -202,6 +210,10 @@ static inline u64 audit_get_contid(struct task_struct *tsk) > > } > > > > extern void audit_log_contid(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 u32 audit_enabled; > > #else /* CONFIG_AUDIT */ > > @@ -271,6 +283,13 @@ static inline u64 audit_get_contid(struct task_struct *tsk) > > > > static inline void audit_log_contid(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) > > +{ } > > > > #define audit_enabled AUDIT_OFF > > #endif /* CONFIG_AUDIT */ > > diff --git a/kernel/audit.c b/kernel/audit.c > > index cf448599ef34..7fa3194f5342 100644 > > --- a/kernel/audit.c > > +++ b/kernel/audit.c > > @@ -72,6 +72,7 @@ > > #include <linux/freezer.h> > > #include <linux/pid_namespace.h> > > #include <net/netns/generic.h> > > +#include <net/net_namespace.h> > > > > #include "audit.h" > > > > @@ -99,9 +100,13 @@ > > /** > > * 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; > > }; > > > > /** > > @@ -275,8 +280,11 @@ 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. > > */ > > @@ -376,6 +384,73 @@ 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 = net_generic(net, audit_net_id); > > + struct list_head *contid_list = &aunet->contid_list; > > + struct audit_contid *cont; > > + > > + if (!audit_contid_valid(contid)) > > + return; > > + if (!aunet) > > + return; > > + spin_lock(&aunet->contid_list_lock); > > + if (!list_empty(contid_list)) > > + list_for_each_entry_rcu(cont, contid_list, list) > > + if (cont->id == contid) { > > + refcount_inc(&cont->refcount); > > + goto out; > > + } > > + cont = kmalloc(sizeof(struct audit_contid), GFP_ATOMIC); > > + if (cont) { > > + INIT_LIST_HEAD(&cont->list); > > + cont->id = contid; > > + refcount_set(&cont->refcount, 1); > > + list_add_rcu(&cont->list, contid_list); > > + } > > +out: > > + spin_unlock(&aunet->contid_list_lock); > > +} > > + > > +void audit_netns_contid_del(struct net *net, u64 contid) > > +{ > > + struct audit_net *aunet; > > + struct list_head *contid_list; > > + struct audit_contid *cont = NULL; > > + > > + if (!net) > > + return; > > + if (!audit_contid_valid(contid)) > > + return; > > + aunet = net_generic(net, audit_net_id); > > + if (!aunet) > > + return; > > + contid_list = &aunet->contid_list; > > + spin_lock(&aunet->contid_list_lock); > > + if (!list_empty(contid_list)) > > + list_for_each_entry_rcu(cont, contid_list, list) > > + if (cont->id == contid) { > > + if (refcount_dec_and_test(&cont->refcount)) { > > + list_del_rcu(&cont->list); > > + kfree_rcu(cont, rcu); > > + } > > + break; > > + } > > + spin_unlock(&aunet->contid_list_lock); > > +} > > + > > +void audit_switch_task_namespaces(struct nsproxy *ns, struct task_struct *p) > > +{ > > + u64 contid = audit_get_contid(p); > > + struct nsproxy *new = p->nsproxy; > > + > > + if (!audit_contid_valid(contid)) > > + return; > > + audit_netns_contid_del(ns->net_ns, contid); > > + if (new) > > + audit_netns_contid_add(new->net_ns, contid); > > +} > > + > > void audit_panic(const char *message) > > { > > switch (audit_failure) { > > @@ -1619,7 +1694,6 @@ 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); > > @@ -1628,7 +1702,8 @@ static int __net_init audit_net_init(struct net *net) > > return -ENOMEM; > > } > > aunet->sk->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT; > > - > > + INIT_LIST_HEAD(&aunet->contid_list); > > + spin_lock_init(&aunet->contid_list_lock); > > return 0; > > } > > > > @@ -2380,6 +2455,7 @@ int audit_set_contid(struct task_struct *task, u64 contid) > > uid_t uid; > > struct tty_struct *tty; > > char comm[sizeof(current->comm)]; > > + struct net *net = task->nsproxy->net_ns; > > > > task_lock(task); > > /* Can't set if audit disabled */ > > @@ -2401,8 +2477,12 @@ int audit_set_contid(struct task_struct *task, u64 contid) > > else if (!(thread_group_leader(task) && thread_group_empty(task))) > > rc = -EALREADY; > > read_unlock(&tasklist_lock); > > - if (!rc) > > + if (!rc) { > > + if (audit_contid_valid(oldcontid)) > > + audit_netns_contid_del(net, oldcontid); > > task->audit->contid = contid; > > + audit_netns_contid_add(net, contid); > > + } > > task_unlock(task); > > > > if (!audit_enabled) > > diff --git a/kernel/nsproxy.c b/kernel/nsproxy.c > > index f6c5d330059a..718b1201ae70 100644 > > --- a/kernel/nsproxy.c > > +++ b/kernel/nsproxy.c > > @@ -27,6 +27,7 @@ > > #include <linux/syscalls.h> > > #include <linux/cgroup.h> > > #include <linux/perf_event.h> > > +#include <linux/audit.h> > > > > static struct kmem_cache *nsproxy_cachep; > > > > @@ -140,6 +141,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk) > > struct nsproxy *old_ns = tsk->nsproxy; > > struct user_namespace *user_ns = task_cred_xxx(tsk, user_ns); > > struct nsproxy *new_ns; > > + u64 contid = audit_get_contid(tsk); > > > > if (likely(!(flags & (CLONE_NEWNS | CLONE_NEWUTS | CLONE_NEWIPC | > > CLONE_NEWPID | CLONE_NEWNET | > > @@ -167,6 +169,7 @@ int copy_namespaces(unsigned long flags, struct task_struct *tsk) > > return PTR_ERR(new_ns); > > > > tsk->nsproxy = new_ns; > > + audit_netns_contid_add(new_ns->net_ns, contid); > > return 0; > > } > > > > @@ -224,6 +227,7 @@ void switch_task_namespaces(struct task_struct *p, struct nsproxy *new) > > ns = p->nsproxy; > > p->nsproxy = new; > > task_unlock(p); > > + audit_switch_task_namespaces(ns, p); > > Since we call audit_switch_task_namespaces() after task_unlock(), > could there be a potential race condition? I'm not going to dive too > much into this now, because it's getting late here, but on first look > it seems like p->nsproxy could change under our hands before we fetch > it in audit_switch_task_namespaces()... The rules are defined in include/linux/nsproxy.h. Since the callers (sys_setns, do_exit, copy_process error path) are all current or handing it a dead task and we are not writing nsproxy or its pointers, which is only allowed by current anyway, we don't need the lock.

> > > > if (ns && atomic_dec_and_test(&ns->count)) > > free_nsproxy(ns); > > -- > > 1.8.3.1 > > Ondrej Mosnacek <omosnace at redhat dot com> - RGB -- Richard Guy Briggs <rgb(a)redhat.com&gt; 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