[PATCH 06/20] audit: make kauditd_task per audit namespace

Gao feng
2013-10-24T07:31:51Z

kauditd_task is used to send audit netlink messages
to the user space auditd process. Because the netlink
messages are per audit namespace, we should make
kaudit_task per auditns to operate the right netlink
skb.

Signed-off-by: Gao feng <gaofeng-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
---
include/linux/audit_namespace.h | 12 +++++++++++
kernel/audit.c | 47 +++++++++++++++++++++++++++--------------
2 files changed, 43 insertions(+), 16 deletions(-)

diff --git a/include/linux/audit_namespace.h b/include/linux/audit_namespace.h
index fdbb6c1..2c0eede 100644
--- a/include/linux/audit_namespace.h
+++ b/include/linux/audit_namespace.h
@@ -15,6 +15,7 @@ struct audit_namespace {
struct sk_buff_head queue;
/* queue of skbs to send to auditd when/if it comes back */
struct sk_buff_head hold_queue;
+ struct task_struct *kauditd_task;
};

extern struct audit_namespace init_audit_ns;
@@ -35,6 +36,17 @@ void put_audit_ns(struct audit_namespace *ns)
skb_queue_purge(&ns->queue);
skb_queue_purge(&ns->hold_queue);
kfree(ns);
+ } else if (atomic_read(&ns->count) == 1) {
+ /* If the last user of audit namespace is kauditd,
+ * we should wake up kauditd and let it kill itself,
+ * Then this audit namespace will be destroyed. */
+ struct task_struct *task;
+
+ rcu_read_lock();
+ task = ACCESS_ONCE(ns->kauditd_task);
+ if (task)
+ wake_up_process(task);
+ rcu_read_unlock();
}
}
#else
diff --git a/kernel/audit.c b/kernel/audit.c
index e5e8cb1..ceb1cbd 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -133,7 +133,6 @@ static DEFINE_SPINLOCK(audit_freelist_lock);
static int audit_freelist_count;
static LIST_HEAD(audit_freelist);

-static struct task_struct *kauditd_task;
static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
static DECLARE_WAIT_QUEUE_HEAD(audit_backlog_wait);

@@ -410,20 +409,20 @@ static void kauditd_send_skb(struct sk_buff *skb)
* in 5 years when I want to play with this again I'll see this
* note and still have no friggin idea what i'm thinking today.
*/
-static void flush_hold_queue(void)
+static void flush_hold_queue(struct audit_namespace *ns)
{
struct sk_buff *skb;

- if (!audit_default || !init_audit_ns.pid)
+ if (!audit_default || !ns->pid)
return;

- skb = skb_dequeue(&init_audit_ns.hold_queue);
+ skb = skb_dequeue(&ns->hold_queue);
if (likely(!skb))
return;

- while (skb && init_audit_ns.pid) {
+ while (skb && ns->pid) {
kauditd_send_skb(skb);
- skb = skb_dequeue(&init_audit_ns.hold_queue);
+ skb = skb_dequeue(&ns->hold_queue);
}

/*
@@ -436,17 +435,25 @@ static void flush_hold_queue(void)

static int kauditd_thread(void *dummy)
{
+ struct audit_namespace *ns = (struct audit_namespace *)dummy;
+
set_freezable();
while (!kthread_should_stop()) {
struct sk_buff *skb;
DECLARE_WAITQUEUE(wait, current);

- flush_hold_queue();
+ /* Ok, We are the last user of this audit namespace,
+ * it's time to go. Kill kauditd thread and release
+ * the audit namespace. */
+ if (atomic_read(&ns->count) == 1)
+ break;
+
+ flush_hold_queue(ns);

- skb = skb_dequeue(&init_audit_ns.queue);
+ skb = skb_dequeue(&ns->queue);
wake_up(&audit_backlog_wait);
if (skb) {
- if (init_audit_ns.pid)
+ if (ns->pid)
kauditd_send_skb(skb);
else
audit_printk_skb(skb);
@@ -455,7 +462,7 @@ static int kauditd_thread(void *dummy)
set_current_state(TASK_INTERRUPTIBLE);
add_wait_queue(&kauditd_wait, &wait);

- if (!skb_queue_len(&init_audit_ns.queue)) {
+ if (!skb_queue_len(&ns->queue)) {
try_to_freeze();
schedule();
}
@@ -463,6 +470,9 @@ static int kauditd_thread(void *dummy)
__set_current_state(TASK_RUNNING);
remove_wait_queue(&kauditd_wait, &wait);
}
+
+ ns->kauditd_task = NULL;
+ put_audit_ns(ns);
return 0;
}

@@ -635,6 +645,7 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)
u16 msg_type = nlh->nlmsg_type;
struct audit_sig_info *sig_data;
char *ctx = NULL;
+ struct audit_namespace *ns = current_audit_ns();
u32 len;

err = audit_netlink_ok(skb, msg_type);
@@ -643,13 +654,16 @@ static int audit_receive_msg(struct sk_buff *skb, struct nlmsghdr *nlh)

/* As soon as there's any sign of userspace auditd,
* start kauditd to talk to it */
- if (!kauditd_task) {
- kauditd_task = kthread_run(kauditd_thread, NULL, "kauditd");
- if (IS_ERR(kauditd_task)) {
- err = PTR_ERR(kauditd_task);
- kauditd_task = NULL;
- return err;
+ if (!ns->kauditd_task) {
+ struct task_struct *tsk;
+ tsk = kthread_run(kauditd_thread,
+ get_audit_ns(ns), "kauditd");
+ if (IS_ERR(tsk)) {
+ put_audit_ns(ns);
+ return PTR_ERR(tsk);
}
+
+ ns->kauditd_task = tsk;
}
seq = nlh->nlmsg_seq;
data = nlmsg_data(nlh);
@@ -930,6 +944,7 @@ static int __init audit_init(void)
audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;

init_audit_ns.pid = 0;
+ init_audit_ns.kauditd_task = NULL;
skb_queue_head_init(&init_audit_ns.queue);
skb_queue_head_init(&init_audit_ns.hold_queue);
audit_initialized = AUDIT_INITIALIZED;
--
1.8.3.1