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-rw-r--r--security/keys/user_defined.c85
1 files changed, 61 insertions, 24 deletions
diff --git a/security/keys/user_defined.c b/security/keys/user_defined.c
index 8d65b3a..c33d361 100644
--- a/security/keys/user_defined.c
+++ b/security/keys/user_defined.c
@@ -42,12 +42,19 @@ struct key_type key_type_user = {
.read = user_read,
};
+struct user_key_payload {
+ struct rcu_head rcu; /* RCU destructor */
+ unsigned short datalen; /* length of this data */
+ char data[0]; /* actual data */
+};
+
/*****************************************************************************/
/*
* instantiate a user defined key
*/
static int user_instantiate(struct key *key, const void *data, size_t datalen)
{
+ struct user_key_payload *upayload;
int ret;
ret = -EINVAL;
@@ -58,13 +65,15 @@ static int user_instantiate(struct key *key, const void *data, size_t datalen)
if (ret < 0)
goto error;
- /* attach the data */
ret = -ENOMEM;
- key->payload.data = kmalloc(datalen, GFP_KERNEL);
- if (!key->payload.data)
+ upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
+ if (!upayload)
goto error;
- memcpy(key->payload.data, data, datalen);
+ /* attach the data */
+ upayload->datalen = datalen;
+ memcpy(upayload->data, data, datalen);
+ rcu_assign_pointer(key->payload.data, upayload);
ret = 0;
error:
@@ -75,18 +84,25 @@ static int user_instantiate(struct key *key, const void *data, size_t datalen)
/*****************************************************************************/
/*
* duplicate a user defined key
+ * - both keys' semaphores are locked against further modification
+ * - the new key cannot yet be accessed
*/
static int user_duplicate(struct key *key, const struct key *source)
{
+ struct user_key_payload *upayload, *spayload;
int ret;
/* just copy the payload */
ret = -ENOMEM;
- key->payload.data = kmalloc(source->datalen, GFP_KERNEL);
+ upayload = kmalloc(sizeof(*upayload) + source->datalen, GFP_KERNEL);
+ if (upayload) {
+ spayload = rcu_dereference(source->payload.data);
+ BUG_ON(source->datalen != spayload->datalen);
- if (key->payload.data) {
- key->datalen = source->datalen;
- memcpy(key->payload.data, source->payload.data, source->datalen);
+ upayload->datalen = key->datalen = spayload->datalen;
+ memcpy(upayload->data, spayload->data, key->datalen);
+
+ key->payload.data = upayload;
ret = 0;
}
@@ -96,40 +112,54 @@ static int user_duplicate(struct key *key, const struct key *source)
/*****************************************************************************/
/*
+ * dispose of the old data from an updated user defined key
+ */
+static void user_update_rcu_disposal(struct rcu_head *rcu)
+{
+ struct user_key_payload *upayload;
+
+ upayload = container_of(rcu, struct user_key_payload, rcu);
+
+ kfree(upayload);
+
+} /* end user_update_rcu_disposal() */
+
+/*****************************************************************************/
+/*
* update a user defined key
+ * - the key's semaphore is write-locked
*/
static int user_update(struct key *key, const void *data, size_t datalen)
{
- void *new, *zap;
+ struct user_key_payload *upayload, *zap;
int ret;
ret = -EINVAL;
if (datalen <= 0 || datalen > 32767 || !data)
goto error;
- /* copy the data */
+ /* construct a replacement payload */
ret = -ENOMEM;
- new = kmalloc(datalen, GFP_KERNEL);
- if (!new)
+ upayload = kmalloc(sizeof(*upayload) + datalen, GFP_KERNEL);
+ if (!upayload)
goto error;
- memcpy(new, data, datalen);
+ upayload->datalen = datalen;
+ memcpy(upayload->data, data, datalen);
/* check the quota and attach the new data */
- zap = new;
- write_lock(&key->lock);
+ zap = upayload;
ret = key_payload_reserve(key, datalen);
if (ret == 0) {
/* attach the new data, displacing the old */
zap = key->payload.data;
- key->payload.data = new;
+ rcu_assign_pointer(key->payload.data, upayload);
key->expiry = 0;
}
- write_unlock(&key->lock);
- kfree(zap);
+ call_rcu(&zap->rcu, user_update_rcu_disposal);
error:
return ret;
@@ -152,13 +182,15 @@ static int user_match(const struct key *key, const void *description)
*/
static void user_destroy(struct key *key)
{
- kfree(key->payload.data);
+ struct user_key_payload *upayload = key->payload.data;
+
+ kfree(upayload);
} /* end user_destroy() */
/*****************************************************************************/
/*
- * describe the user
+ * describe the user key
*/
static void user_describe(const struct key *key, struct seq_file *m)
{
@@ -171,18 +203,23 @@ static void user_describe(const struct key *key, struct seq_file *m)
/*****************************************************************************/
/*
* read the key data
+ * - the key's semaphore is read-locked
*/
static long user_read(const struct key *key,
char __user *buffer, size_t buflen)
{
- long ret = key->datalen;
+ struct user_key_payload *upayload;
+ long ret;
+
+ upayload = rcu_dereference(key->payload.data);
+ ret = upayload->datalen;
/* we can return the data as is */
if (buffer && buflen > 0) {
- if (buflen > key->datalen)
- buflen = key->datalen;
+ if (buflen > upayload->datalen)
+ buflen = upayload->datalen;
- if (copy_to_user(buffer, key->payload.data, buflen) != 0)
+ if (copy_to_user(buffer, upayload->data, buflen) != 0)
ret = -EFAULT;
}
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