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NetLabel: fix a cache race condition

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Testing revealed a problem with the NetLabel cache where a cached entry could
be freed while in use by the LSM layer causing an oops and other problems.
This patch fixes that problem by introducing a reference counter to the cache
entry so that it is only freed when it is no longer in use.

Signed-off-by: Paul Moore <paul.moore@hp.com>
Signed-off-by: James Morris <jmorris@namei.org>
This commit is contained in:
paul.moore@hp.com
2006-10-04 11:46:31 -04:00
committed by David S. Miller
parent c25d518044
commit ffb733c650
4 changed files with 79 additions and 40 deletions
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18
net/ipv4/cipso_ipv4.c
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@@ -43,6 +43,7 @@
#include <net/tcp.h>
#include <net/netlabel.h>
#include <net/cipso_ipv4.h>
#include <asm/atomic.h>
#include <asm/bug.h>
struct cipso_v4_domhsh_entry {
@@ -79,7 +80,7 @@ struct cipso_v4_map_cache_entry {
unsigned char *key;
size_t key_len;
struct netlbl_lsm_cache lsm_data;
struct netlbl_lsm_cache *lsm_data;
u32 activity;
struct list_head list;
@@ -188,13 +189,14 @@ static void cipso_v4_doi_domhsh_free(struct rcu_head *entry)
* @entry: the entry to free
*
* Description:
* This function frees the memory associated with a cache entry.
* This function frees the memory associated with a cache entry including the
* LSM cache data if there are no longer any users, i.e. reference count == 0.
*
*/
static void cipso_v4_cache_entry_free(struct cipso_v4_map_cache_entry *entry)
{
if (entry->lsm_data.free)
entry->lsm_data.free(entry->lsm_data.data);
if (entry->lsm_data)
netlbl_secattr_cache_free(entry->lsm_data);
kfree(entry->key);
kfree(entry);
}
@@ -315,8 +317,8 @@ static int cipso_v4_cache_check(const unsigned char *key,
entry->key_len == key_len &&
memcmp(entry->key, key, key_len) == 0) {
entry->activity += 1;
secattr->cache.free = entry->lsm_data.free;
secattr->cache.data = entry->lsm_data.data;
atomic_inc(&entry->lsm_data->refcount);
secattr->cache = entry->lsm_data;
if (prev_entry == NULL) {
spin_unlock_bh(&cipso_v4_cache[bkt].lock);
return 0;
@@ -383,8 +385,8 @@ int cipso_v4_cache_add(const struct sk_buff *skb,
memcpy(entry->key, cipso_ptr, cipso_ptr_len);
entry->key_len = cipso_ptr_len;
entry->hash = cipso_v4_map_cache_hash(cipso_ptr, cipso_ptr_len);
entry->lsm_data.free = secattr->cache.free;
entry->lsm_data.data = secattr->cache.data;
atomic_inc(&secattr->cache->refcount);
entry->lsm_data = secattr->cache;
bkt = entry->hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
spin_lock_bh(&cipso_v4_cache[bkt].lock);