NetLabel: fix a cache race condition
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
David S. Miller
parent
c25d518044
commit
ffb733c650
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@ -34,6 +34,7 @@
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#include <linux/net.h>
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#include <linux/skbuff.h>
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#include <net/netlink.h>
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#include <asm/atomic.h>
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/*
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* NetLabel - A management interface for maintaining network packet label
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@ -106,6 +107,7 @@ int netlbl_domhsh_remove(const char *domain, struct netlbl_audit *audit_info);
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/* LSM security attributes */
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struct netlbl_lsm_cache {
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atomic_t refcount;
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void (*free) (const void *data);
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void *data;
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};
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@ -117,7 +119,7 @@ struct netlbl_lsm_secattr {
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unsigned char *mls_cat;
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size_t mls_cat_len;
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struct netlbl_lsm_cache cache;
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struct netlbl_lsm_cache *cache;
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};
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/*
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@ -125,6 +127,43 @@ struct netlbl_lsm_secattr {
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*/
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/**
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* netlbl_secattr_cache_alloc - Allocate and initialize a secattr cache
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* @flags: the memory allocation flags
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*
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* Description:
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* Allocate and initialize a netlbl_lsm_cache structure. Returns a pointer
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* on success, NULL on failure.
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*
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*/
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static inline struct netlbl_lsm_cache *netlbl_secattr_cache_alloc(int flags)
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{
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struct netlbl_lsm_cache *cache;
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cache = kzalloc(sizeof(*cache), flags);
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if (cache)
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atomic_set(&cache->refcount, 1);
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return cache;
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}
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/**
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* netlbl_secattr_cache_free - Frees a netlbl_lsm_cache struct
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* @cache: the struct to free
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*
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* Description:
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* Frees @secattr including all of the internal buffers.
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*
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*/
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static inline void netlbl_secattr_cache_free(struct netlbl_lsm_cache *cache)
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{
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if (!atomic_dec_and_test(&cache->refcount))
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return;
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if (cache->free)
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cache->free(cache->data);
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kfree(cache);
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}
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/**
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* netlbl_secattr_init - Initialize a netlbl_lsm_secattr struct
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* @secattr: the struct to initialize
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@ -143,20 +182,16 @@ static inline int netlbl_secattr_init(struct netlbl_lsm_secattr *secattr)
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/**
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* netlbl_secattr_destroy - Clears a netlbl_lsm_secattr struct
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* @secattr: the struct to clear
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* @clear_cache: cache clear flag
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*
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* Description:
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* Destroys the @secattr struct, including freeing all of the internal buffers.
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* If @clear_cache is true then free the cache fields, otherwise leave them
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* intact. The struct must be reset with a call to netlbl_secattr_init()
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* before reuse.
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* The struct must be reset with a call to netlbl_secattr_init() before reuse.
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*
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*/
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static inline void netlbl_secattr_destroy(struct netlbl_lsm_secattr *secattr,
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u32 clear_cache)
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static inline void netlbl_secattr_destroy(struct netlbl_lsm_secattr *secattr)
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{
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if (clear_cache && secattr->cache.data != NULL && secattr->cache.free)
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secattr->cache.free(secattr->cache.data);
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if (secattr->cache)
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netlbl_secattr_cache_free(secattr->cache);
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kfree(secattr->domain);
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kfree(secattr->mls_cat);
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}
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@ -178,17 +213,14 @@ static inline struct netlbl_lsm_secattr *netlbl_secattr_alloc(int flags)
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/**
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* netlbl_secattr_free - Frees a netlbl_lsm_secattr struct
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* @secattr: the struct to free
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* @clear_cache: cache clear flag
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*
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* Description:
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* Frees @secattr including all of the internal buffers. If @clear_cache is
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* true then free the cache fields, otherwise leave them intact.
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* Frees @secattr including all of the internal buffers.
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*
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*/
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static inline void netlbl_secattr_free(struct netlbl_lsm_secattr *secattr,
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u32 clear_cache)
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static inline void netlbl_secattr_free(struct netlbl_lsm_secattr *secattr)
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{
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netlbl_secattr_destroy(secattr, clear_cache);
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netlbl_secattr_destroy(secattr);
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kfree(secattr);
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}
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@ -43,6 +43,7 @@
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#include <net/tcp.h>
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#include <net/netlabel.h>
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#include <net/cipso_ipv4.h>
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#include <asm/atomic.h>
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#include <asm/bug.h>
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struct cipso_v4_domhsh_entry {
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@ -79,7 +80,7 @@ struct cipso_v4_map_cache_entry {
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unsigned char *key;
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size_t key_len;
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struct netlbl_lsm_cache lsm_data;
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struct netlbl_lsm_cache *lsm_data;
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u32 activity;
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struct list_head list;
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@ -188,13 +189,14 @@ static void cipso_v4_doi_domhsh_free(struct rcu_head *entry)
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* @entry: the entry to free
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*
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* Description:
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* This function frees the memory associated with a cache entry.
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* This function frees the memory associated with a cache entry including the
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* LSM cache data if there are no longer any users, i.e. reference count == 0.
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*
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*/
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static void cipso_v4_cache_entry_free(struct cipso_v4_map_cache_entry *entry)
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{
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if (entry->lsm_data.free)
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entry->lsm_data.free(entry->lsm_data.data);
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if (entry->lsm_data)
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netlbl_secattr_cache_free(entry->lsm_data);
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kfree(entry->key);
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kfree(entry);
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}
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@ -315,8 +317,8 @@ static int cipso_v4_cache_check(const unsigned char *key,
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entry->key_len == key_len &&
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memcmp(entry->key, key, key_len) == 0) {
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entry->activity += 1;
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secattr->cache.free = entry->lsm_data.free;
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secattr->cache.data = entry->lsm_data.data;
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atomic_inc(&entry->lsm_data->refcount);
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secattr->cache = entry->lsm_data;
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if (prev_entry == NULL) {
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spin_unlock_bh(&cipso_v4_cache[bkt].lock);
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return 0;
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@ -383,8 +385,8 @@ int cipso_v4_cache_add(const struct sk_buff *skb,
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memcpy(entry->key, cipso_ptr, cipso_ptr_len);
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entry->key_len = cipso_ptr_len;
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entry->hash = cipso_v4_map_cache_hash(cipso_ptr, cipso_ptr_len);
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entry->lsm_data.free = secattr->cache.free;
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entry->lsm_data.data = secattr->cache.data;
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atomic_inc(&secattr->cache->refcount);
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entry->lsm_data = secattr->cache;
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bkt = entry->hash & (CIPSO_V4_CACHE_BUCKETBITS - 1);
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spin_lock_bh(&cipso_v4_cache[bkt].lock);
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@ -200,7 +200,7 @@ void netlbl_cache_invalidate(void)
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int netlbl_cache_add(const struct sk_buff *skb,
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const struct netlbl_lsm_secattr *secattr)
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{
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if (secattr->cache.data == NULL)
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if (secattr->cache == NULL)
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return -ENOMSG;
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if (CIPSO_V4_OPTEXIST(skb))
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@ -2172,7 +2172,12 @@ struct netlbl_cache {
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*/
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static void selinux_netlbl_cache_free(const void *data)
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{
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struct netlbl_cache *cache = NETLBL_CACHE(data);
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struct netlbl_cache *cache;
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if (data == NULL)
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return;
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cache = NETLBL_CACHE(data);
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switch (cache->type) {
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case NETLBL_CACHE_T_MLS:
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ebitmap_destroy(&cache->data.mls_label.level[0].cat);
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@ -2197,17 +2202,20 @@ static void selinux_netlbl_cache_add(struct sk_buff *skb, struct context *ctx)
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struct netlbl_lsm_secattr secattr;
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netlbl_secattr_init(&secattr);
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secattr.cache = netlbl_secattr_cache_alloc(GFP_ATOMIC);
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if (secattr.cache == NULL)
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goto netlbl_cache_add_return;
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cache = kzalloc(sizeof(*cache), GFP_ATOMIC);
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if (cache == NULL)
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goto netlbl_cache_add_failure;
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secattr.cache.free = selinux_netlbl_cache_free;
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secattr.cache.data = (void *)cache;
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goto netlbl_cache_add_return;
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secattr.cache->free = selinux_netlbl_cache_free;
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secattr.cache->data = (void *)cache;
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cache->type = NETLBL_CACHE_T_MLS;
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if (ebitmap_cpy(&cache->data.mls_label.level[0].cat,
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&ctx->range.level[0].cat) != 0)
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goto netlbl_cache_add_failure;
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goto netlbl_cache_add_return;
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cache->data.mls_label.level[1].cat.highbit =
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cache->data.mls_label.level[0].cat.highbit;
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cache->data.mls_label.level[1].cat.node =
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@ -2215,13 +2223,10 @@ static void selinux_netlbl_cache_add(struct sk_buff *skb, struct context *ctx)
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cache->data.mls_label.level[0].sens = ctx->range.level[0].sens;
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cache->data.mls_label.level[1].sens = ctx->range.level[0].sens;
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if (netlbl_cache_add(skb, &secattr) != 0)
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goto netlbl_cache_add_failure;
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netlbl_cache_add(skb, &secattr);
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return;
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netlbl_cache_add_failure:
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netlbl_secattr_destroy(&secattr, 1);
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netlbl_cache_add_return:
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netlbl_secattr_destroy(&secattr);
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}
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/**
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@ -2263,8 +2268,8 @@ static int selinux_netlbl_secattr_to_sid(struct sk_buff *skb,
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POLICY_RDLOCK;
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if (secattr->cache.data) {
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cache = NETLBL_CACHE(secattr->cache.data);
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if (secattr->cache) {
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cache = NETLBL_CACHE(secattr->cache->data);
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switch (cache->type) {
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case NETLBL_CACHE_T_SID:
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*sid = cache->data.sid;
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@ -2369,7 +2374,7 @@ static int selinux_netlbl_skbuff_getsid(struct sk_buff *skb,
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&secattr,
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base_sid,
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sid);
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netlbl_secattr_destroy(&secattr, 0);
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netlbl_secattr_destroy(&secattr);
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return rc;
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}
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@ -2415,7 +2420,7 @@ static int selinux_netlbl_socket_setsid(struct socket *sock, u32 sid)
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if (rc == 0)
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sksec->nlbl_state = NLBL_LABELED;
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netlbl_secattr_destroy(&secattr, 0);
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netlbl_secattr_destroy(&secattr);
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netlbl_socket_setsid_return:
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POLICY_RDUNLOCK;
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@ -2517,7 +2522,7 @@ void selinux_netlbl_sock_graft(struct sock *sk, struct socket *sock)
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sksec->sid,
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&nlbl_peer_sid) == 0)
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sksec->peer_sid = nlbl_peer_sid;
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netlbl_secattr_destroy(&secattr, 0);
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netlbl_secattr_destroy(&secattr);
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sksec->nlbl_state = NLBL_REQUIRE;
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