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

On Fri, Mar 15, 2019 at 2:35 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/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; We should move the contid_list assignment below this check, or decide that aunet is always going to valid (?) and get rid of this check completely.

> + spin_lock(&aunet->contid_list_lock); > + if (!list_empty(contid_list)) We don't need the list_empty() check here do we? I think we can just call list_for_each_entry_rcu(), yes?

> + 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 you had to guess, what do you think is going to be more common: bumping the refcount of an existing entry in the list, or adding a new entry? I'm asking because I always get a little nervous when doing allocations while holding a spinlock. Yes, you are doing it with GFP_ATOMIC, but it still seems like something to try and avoid if this is going to approach 50%. However, if the new entry is rare then the extra work of always doing the allocation before taking the lock and then freeing it afterwards might be a bad tradeoff. My gut feeling says we might do about as many allocations as refcount bumps, but I could be thinking about this wrong.

Moving the allocation outside the spinlock might also open the door to doing this as GFP_KERNEL, which is a good thing, but I haven't looked at the callers to see if that is possible (it may not be). That's an exercise left to the patch author (if he hasn't done that already).

> + if (cont) { > + INIT_LIST_HEAD(&cont->list); Unless there is some guidance that INIT_LIST_HEAD() should be used regardless, you shouldn't need to call this here since list_add_rcu() will take care of any list.h related initialization.

> + cont->id = contid; > + refcount_set(&cont->refcount, 1); > + list_add_rcu(&cont->list, contid_list); > + } > +out: > + spin_unlock(&aunet->contid_list_lock); > +} paul moore