On Tue, Apr 02, 2019 at 09:31:49AM -0400, Paul Moore wrote: > On Tue, Apr 2, 2019 at 7:32 AM Neil Horman <nhorman@xxxxxxxxxxxxx> wrote: > > On Mon, Apr 01, 2019 at 10:50:03AM -0400, Paul Moore wrote: > > > On Fri, Mar 15, 2019 at 2:35 PM Richard Guy Briggs <rgb@xxxxxxxxxx> 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@xxxxxxxxxx> > > > > --- > > > > 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. > > > > > I'm not sure why that would be needed. Finding the net_id list is an operation > > of a map relating net namespaces to lists, not contids to lists. We could do > > it, sure, but since they're unrelated operations, I don't think we experience > > any slowdowns from doing it this way. > > In the first line of the function, when aunet is declared, it is also > assigned a value using net_generic(): > > struct audit_net *aunet = net_generic(net, audit_net_id); > > Later in the function there is check to see if aunet is NULL, yet on > the second line of the function (before the NULL check), there is this > line of code: > > struct list_head *contid_list = &aunet->contid_list; > > ... which could result in the dereference of a NULL pointer if aunet > is NULL. My suggestion was either to move this assignment below the > aunet-NULL check or decide that aunet was always going to be valid > (e.g. non-NULL) and do away with the aunet-NULL check completely. > Richard has since replied that the aunet-NULL check has been > demonstrated to be necessary so the proper thing to do would be to > move the assignment. I believe that is what Richard is planning on > doing. > oh, I'm sorry, you're right, I was looking at the contid tests not the list tests. Neil > > > > + 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. > > > > There is a corner case that needs it. list_add_rcu has a check that gets > > called, __list_add_valid. Its a noop in the regular case, but if > > CONFIG_DEBUG_LIST is defined, its a check to ensure that the next and prev > > pointers getting passed in aren't set to detectable corrupt values. If we pass > > in garbage, we can get transient false positives on that check, so we need to > > set the list pointers to known good values before hand, either by using kzalloc, > > or INIT_LIST_HEAD, as has been done here. Given that we expressly set every > > field of this structure, I think this is the right approach, as it uses the list > > macro to expressly set the list values to their proper state. > > Good to know, thanks. > > -- > paul moore > www.paul-moore.com >
