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Commit 8cc96382 authored by Paul Moore's avatar Paul Moore
Browse files

audit: use kmem_cache to manage the audit_buffer cache 



The audit subsystem implemented its own buffer cache mechanism which
is a bit silly these days when we could use the kmem_cache construct.

Some credit is due to Florian Westphal for originally proposing that
we remove the audit cache implementation in favor of simple
kmalloc()/kfree() calls, but I would rather have a dedicated slab
cache to ease debugging and future stats/performance work.

Cc: Florian Westphal <fw@strlen.de>
Reviewed-by: default avatarRichard Guy Briggs <rgb@redhat.com>
Signed-off-by: default avatarPaul Moore <paul@paul-moore.com>
parent 2115bb25

kernel/audit.c

+17 −49
Original line number Diff line number Diff line
@@ -59,6 +59,7 @@ 
#include <linux/mutex.h>

#include <linux/gfp.h>

#include <linux/pid.h>

#include <linux/slab.h>



#include <linux/audit.h>
@@ -152,12 +153,7 @@ static atomic_t audit_lost = ATOMIC_INIT(0); 
/* Hash for inode-based rules */

struct list_head audit_inode_hash[AUDIT_INODE_BUCKETS];



/* 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_freelist_lock);

static int	   audit_freelist_count;

static LIST_HEAD(audit_freelist);

static struct kmem_cache *audit_buffer_cache;



/* queue msgs to send via kauditd_task */

static struct sk_buff_head audit_queue;
@@ -192,17 +188,12 @@ DEFINE_MUTEX(audit_cmd_mutex); 
 * should be at least that large. */

#define AUDIT_BUFSIZ 1024



/* AUDIT_MAXFREE is the number of empty audit_buffers we keep on the

 * audit_freelist.  Doing so eliminates many kmalloc/kfree calls. */

#define AUDIT_MAXFREE  (2*NR_CPUS)



/* The audit_buffer is used when formatting an audit record.  The caller

 * locks briefly to get the record off the freelist or to allocate the

 * buffer, and locks briefly to send the buffer to the netlink layer or

 * to place it on a transmit queue.  Multiple audit_buffers can be in

 * use simultaneously. */

struct audit_buffer {

	struct list_head     list;

	struct sk_buff       *skb;	/* formatted skb ready to send */

	struct audit_context *ctx;	/* NULL or associated context */

	gfp_t		     gfp_mask;
@@ -1486,6 +1477,10 @@ static int __init audit_init(void) 
	if (audit_initialized == AUDIT_DISABLED)

		return 0;



	audit_buffer_cache = kmem_cache_create("audit_buffer",

					       sizeof(struct audit_buffer),

					       0, SLAB_PANIC, NULL);



	memset(&auditd_conn, 0, sizeof(auditd_conn));

	spin_lock_init(&auditd_conn.lock);
@@ -1554,60 +1549,33 @@ __setup("audit_backlog_limit=", audit_backlog_limit_set); 


static void audit_buffer_free(struct audit_buffer *ab)

{

	unsigned long flags;



	if (!ab)

		return;



	kfree_skb(ab->skb);

	spin_lock_irqsave(&audit_freelist_lock, flags);

	if (audit_freelist_count > AUDIT_MAXFREE)

		kfree(ab);

	else {

		audit_freelist_count++;

		list_add(&ab->list, &audit_freelist);

	}

	spin_unlock_irqrestore(&audit_freelist_lock, flags);

	kmem_cache_free(audit_buffer_cache, ab);

}



static struct audit_buffer *audit_buffer_alloc(struct audit_context *ctx,

					       gfp_t gfp_mask, int type)

{

	unsigned long flags;

	struct audit_buffer *ab = NULL;

	struct nlmsghdr *nlh;



	spin_lock_irqsave(&audit_freelist_lock, flags);

	if (!list_empty(&audit_freelist)) {

		ab = list_entry(audit_freelist.next,

				struct audit_buffer, list);

		list_del(&ab->list);

		--audit_freelist_count;

	}

	spin_unlock_irqrestore(&audit_freelist_lock, flags);

	struct audit_buffer *ab;



	if (!ab) {

		ab = kmalloc(sizeof(*ab), gfp_mask);

	ab = kmem_cache_alloc(audit_buffer_cache, gfp_mask);

	if (!ab)

			goto err;

	}



	ab->ctx = ctx;

	ab->gfp_mask = gfp_mask;

		return NULL;



	ab->skb = nlmsg_new(AUDIT_BUFSIZ, gfp_mask);

	if (!ab->skb)

		goto err;

	if (!nlmsg_put(ab->skb, 0, 0, type, 0, 0))

		goto err;



	nlh = nlmsg_put(ab->skb, 0, 0, type, 0, 0);

	if (!nlh)

		goto out_kfree_skb;

	ab->ctx = ctx;

	ab->gfp_mask = gfp_mask;



	return ab;



out_kfree_skb:

	kfree_skb(ab->skb);

	ab->skb = NULL;

err:

	audit_buffer_free(ab);

	return NULL;