AUDIT: Send netlink messages from a separate kernel thread
netlink_unicast() will attempt to reallocate and will free messages if
the socket's rcvbuf limit is reached unless we give it an infinite
timeout. So do that, from a kernel thread which is dedicated to spewing
stuff up the netlink socket.
Signed-off-by: David Woodhouse <dwmw2@infradead.org>
diff --git a/kernel/audit.c b/kernel/audit.c
index dae3570..bbc6f54 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -46,6 +46,8 @@
#include <asm/types.h>
#include <linux/mm.h>
#include <linux/module.h>
+#include <linux/err.h>
+#include <linux/kthread.h>
#include <linux/audit.h>
@@ -77,7 +79,6 @@
/* Number of outstanding audit_buffers allowed. */
static int audit_backlog_limit = 64;
-static atomic_t audit_backlog = ATOMIC_INIT(0);
/* The identity of the user shutting down the audit system. */
uid_t audit_sig_uid = -1;
@@ -95,19 +96,17 @@
/* The netlink socket. */
static struct sock *audit_sock;
-/* There are two lists of audit buffers. The txlist contains audit
- * buffers that cannot be sent immediately to the netlink device because
- * we are in an irq context (these are sent later in a tasklet).
- *
- * The second list is a list of pre-allocated audit buffers (if more
+/* The audit_freelist is a list of pre-allocated audit buffers (if more
* than AUDIT_MAXFREE are in use, the audit buffer is freed instead of
* being placed on the freelist). */
-static DEFINE_SPINLOCK(audit_txlist_lock);
static DEFINE_SPINLOCK(audit_freelist_lock);
static int audit_freelist_count = 0;
-static LIST_HEAD(audit_txlist);
static LIST_HEAD(audit_freelist);
+static struct sk_buff_head audit_skb_queue;
+static struct task_struct *kauditd_task;
+static DECLARE_WAIT_QUEUE_HEAD(kauditd_wait);
+
/* There are three lists of rules -- one to search at task creation
* time, one to search at syscall entry time, and another to search at
* syscall exit time. */
@@ -151,9 +150,6 @@
struct audit_rule rule;
};
-static void audit_log_end_irq(struct audit_buffer *ab);
-static void audit_log_end_fast(struct audit_buffer *ab);
-
static void audit_panic(const char *message)
{
switch (audit_failure)
@@ -224,10 +220,8 @@
if (print) {
printk(KERN_WARNING
- "audit: audit_lost=%d audit_backlog=%d"
- " audit_rate_limit=%d audit_backlog_limit=%d\n",
+ "audit: audit_lost=%d audit_rate_limit=%d audit_backlog_limit=%d\n",
atomic_read(&audit_lost),
- atomic_read(&audit_backlog),
audit_rate_limit,
audit_backlog_limit);
audit_panic(message);
@@ -281,6 +275,38 @@
return old;
}
+int kauditd_thread(void *dummy)
+{
+ struct sk_buff *skb;
+
+ while (1) {
+ skb = skb_dequeue(&audit_skb_queue);
+ if (skb) {
+ if (audit_pid) {
+ int err = netlink_unicast(audit_sock, skb, audit_pid, 0);
+ if (err < 0) {
+ BUG_ON(err != -ECONNREFUSED); /* Shoudn't happen */
+ printk(KERN_ERR "audit: *NO* daemon at audit_pid=%d\n", audit_pid);
+ audit_pid = 0;
+ }
+ } else {
+ printk(KERN_ERR "%s\n", skb->data + NLMSG_SPACE(0));
+ kfree_skb(skb);
+ }
+ } else {
+ DECLARE_WAITQUEUE(wait, current);
+ set_current_state(TASK_INTERRUPTIBLE);
+ add_wait_queue(&kauditd_wait, &wait);
+
+ if (!skb_queue_len(&audit_skb_queue))
+ schedule();
+
+ __set_current_state(TASK_RUNNING);
+ remove_wait_queue(&kauditd_wait, &wait);
+ }
+ }
+}
+
void audit_send_reply(int pid, int seq, int type, int done, int multi,
void *payload, int size)
{
@@ -293,13 +319,16 @@
skb = alloc_skb(len, GFP_KERNEL);
if (!skb)
- goto nlmsg_failure;
+ return;
- nlh = NLMSG_PUT(skb, pid, seq, t, len - sizeof(*nlh));
+ nlh = NLMSG_PUT(skb, pid, seq, t, size);
nlh->nlmsg_flags = flags;
data = NLMSG_DATA(nlh);
memcpy(data, payload, size);
- netlink_unicast(audit_sock, skb, pid, MSG_DONTWAIT);
+
+ /* Ignore failure. It'll only happen if the sender goes away,
+ because our timeout is set to infinite. */
+ netlink_unicast(audit_sock, skb, pid, 0);
return;
nlmsg_failure: /* Used by NLMSG_PUT */
@@ -351,6 +380,15 @@
if (err)
return err;
+ /* 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;
+ }
+
pid = NETLINK_CREDS(skb)->pid;
uid = NETLINK_CREDS(skb)->uid;
loginuid = NETLINK_CB(skb).loginuid;
@@ -365,7 +403,7 @@
status_set.rate_limit = audit_rate_limit;
status_set.backlog_limit = audit_backlog_limit;
status_set.lost = atomic_read(&audit_lost);
- status_set.backlog = atomic_read(&audit_backlog);
+ status_set.backlog = skb_queue_len(&audit_skb_queue);
audit_send_reply(NETLINK_CB(skb).pid, seq, AUDIT_GET, 0, 0,
&status_set, sizeof(status_set));
break;
@@ -471,44 +509,6 @@
up(&audit_netlink_sem);
}
-/* Grab skbuff from the audit_buffer and send to user space. */
-static inline int audit_log_drain(struct audit_buffer *ab)
-{
- struct sk_buff *skb = ab->skb;
-
- if (skb) {
- int retval = 0;
-
- if (audit_pid) {
- struct nlmsghdr *nlh = (struct nlmsghdr *)skb->data;
- nlh->nlmsg_len = skb->len - NLMSG_SPACE(0);
- skb_get(skb); /* because netlink_* frees */
- retval = netlink_unicast(audit_sock, skb, audit_pid,
- MSG_DONTWAIT);
- }
- if (retval == -EAGAIN &&
- (atomic_read(&audit_backlog)) < audit_backlog_limit) {
- audit_log_end_irq(ab);
- return 1;
- }
- if (retval < 0) {
- if (retval == -ECONNREFUSED) {
- printk(KERN_ERR
- "audit: *NO* daemon at audit_pid=%d\n",
- audit_pid);
- audit_pid = 0;
- } else
- audit_log_lost("netlink socket too busy");
- }
- if (!audit_pid) { /* No daemon */
- int offset = NLMSG_SPACE(0);
- int len = skb->len - offset;
- skb->data[offset + len] = '\0';
- printk(KERN_ERR "%s\n", skb->data + offset);
- }
- }
- return 0;
-}
/* Initialize audit support at boot time. */
static int __init audit_init(void)
@@ -519,6 +519,8 @@
if (!audit_sock)
audit_panic("cannot initialize netlink socket");
+ audit_sock->sk_sndtimeo = MAX_SCHEDULE_TIMEOUT;
+ skb_queue_head_init(&audit_skb_queue);
audit_initialized = 1;
audit_enabled = audit_default;
audit_log(NULL, AUDIT_KERNEL, "initialized");
@@ -549,7 +551,7 @@
if (ab->skb)
kfree_skb(ab->skb);
- atomic_dec(&audit_backlog);
+
spin_lock_irqsave(&audit_freelist_lock, flags);
if (++audit_freelist_count > AUDIT_MAXFREE)
kfree(ab);
@@ -579,13 +581,12 @@
if (!ab)
goto err;
}
- atomic_inc(&audit_backlog);
ab->skb = alloc_skb(AUDIT_BUFSIZ, gfp_mask);
if (!ab->skb)
goto err;
- ab->ctx = ctx;
+ ab->ctx = ctx;
nlh = (struct nlmsghdr *)skb_put(ab->skb, NLMSG_SPACE(0));
nlh->nlmsg_type = type;
nlh->nlmsg_flags = 0;
@@ -612,18 +613,6 @@
if (!audit_initialized)
return NULL;
- if (audit_backlog_limit
- && atomic_read(&audit_backlog) > audit_backlog_limit) {
- if (audit_rate_check())
- printk(KERN_WARNING
- "audit: audit_backlog=%d > "
- "audit_backlog_limit=%d\n",
- atomic_read(&audit_backlog),
- audit_backlog_limit);
- audit_log_lost("backlog limit exceeded");
- return NULL;
- }
-
ab = audit_buffer_alloc(ctx, GFP_ATOMIC, type);
if (!ab) {
audit_log_lost("out of memory in audit_log_start");
@@ -784,70 +773,30 @@
kfree(path);
}
-/* Remove queued messages from the audit_txlist and send them to user space. */
-static void audit_tasklet_handler(unsigned long arg)
-{
- LIST_HEAD(list);
- struct audit_buffer *ab;
- unsigned long flags;
-
- spin_lock_irqsave(&audit_txlist_lock, flags);
- list_splice_init(&audit_txlist, &list);
- spin_unlock_irqrestore(&audit_txlist_lock, flags);
-
- while (!list_empty(&list)) {
- ab = list_entry(list.next, struct audit_buffer, list);
- list_del(&ab->list);
- audit_log_end_fast(ab);
- }
-}
-
-static DECLARE_TASKLET(audit_tasklet, audit_tasklet_handler, 0);
-
/* The netlink_* functions cannot be called inside an irq context, so
* the audit buffer is places on a queue and a tasklet is scheduled to
* remove them from the queue outside the irq context. May be called in
* any context. */
-static void audit_log_end_irq(struct audit_buffer *ab)
+void audit_log_end(struct audit_buffer *ab)
{
- unsigned long flags;
-
- if (!ab)
- return;
- spin_lock_irqsave(&audit_txlist_lock, flags);
- list_add_tail(&ab->list, &audit_txlist);
- spin_unlock_irqrestore(&audit_txlist_lock, flags);
-
- tasklet_schedule(&audit_tasklet);
-}
-
-/* Send the message in the audit buffer directly to user space. May not
- * be called in an irq context. */
-static void audit_log_end_fast(struct audit_buffer *ab)
-{
- BUG_ON(in_irq());
if (!ab)
return;
if (!audit_rate_check()) {
audit_log_lost("rate limit exceeded");
} else {
- if (audit_log_drain(ab))
- return;
+ if (audit_pid) {
+ struct nlmsghdr *nlh = (struct nlmsghdr *)ab->skb->data;
+ nlh->nlmsg_len = ab->skb->len - NLMSG_SPACE(0);
+ skb_queue_tail(&audit_skb_queue, ab->skb);
+ ab->skb = NULL;
+ wake_up_interruptible(&kauditd_wait);
+ } else {
+ printk("%s\n", ab->skb->data + NLMSG_SPACE(0));
+ }
}
audit_buffer_free(ab);
}
-/* Send or queue the message in the audit buffer, depending on the
- * current context. (A convenience function that may be called in any
- * context.) */
-void audit_log_end(struct audit_buffer *ab)
-{
- if (in_irq())
- audit_log_end_irq(ab);
- else
- audit_log_end_fast(ab);
-}
-
/* Log an audit record. This is a convenience function that calls
* audit_log_start, audit_log_vformat, and audit_log_end. It may be
* called in any context. */