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authorPaul Moore <paul@paul-moore.com>2017-05-02 10:16:05 -0400
committerPaul Moore <paul@paul-moore.com>2017-05-02 10:16:05 -0400
commit8cc96382d9a7fe1746286670dd5140c3b12638ae (patch)
tree22383341416f7ddd97b0f16d259967104ce31739 /kernel
parent2115bb250f260089743e26decfb5f271ba71ca37 (diff)
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: Richard Guy Briggs <rgb@redhat.com> Signed-off-by: Paul Moore <paul@paul-moore.com>
Diffstat (limited to 'kernel')
-rw-r--r--kernel/audit.c66
1 files changed, 17 insertions, 49 deletions
diff --git a/kernel/audit.c b/kernel/audit.c
index 41efd2ad1931..10bc2bad2adf 100644
--- a/kernel/audit.c
+++ b/kernel/audit.c
@@ -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)
+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);
-
- if (!ab) {
- ab = kmalloc(sizeof(*ab), gfp_mask);
- if (!ab)
- goto err;
- }
+ struct audit_buffer *ab;
- ab->ctx = ctx;
- ab->gfp_mask = gfp_mask;
+ ab = kmem_cache_alloc(audit_buffer_cache, gfp_mask);
+ if (!ab)
+ 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;