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-rw-r--r--security/keys/keyring.c41
1 files changed, 22 insertions, 19 deletions
diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index dd7cd0f8e13..1e4b0037935 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -20,6 +20,11 @@
#include <asm/uaccess.h>
#include "internal.h"
+#define rcu_dereference_locked_keyring(keyring) \
+ (rcu_dereference_protected( \
+ (keyring)->payload.subscriptions, \
+ rwsem_is_locked((struct rw_semaphore *)&(keyring)->sem)))
+
/*
* when plumbing the depths of the key tree, this sets a hard limit set on how
* deep we're willing to go
@@ -201,8 +206,7 @@ static long keyring_read(const struct key *keyring,
int loop, ret;
ret = 0;
- klist = keyring->payload.subscriptions;
-
+ klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* calculate how much data we could return */
qty = klist->nkeys * sizeof(key_serial_t);
@@ -526,9 +530,8 @@ struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
struct key *keyring;
int bucket;
- keyring = ERR_PTR(-EINVAL);
if (!name)
- goto error;
+ return ERR_PTR(-EINVAL);
bucket = keyring_hash(name);
@@ -555,17 +558,18 @@ struct key *find_keyring_by_name(const char *name, bool skip_perm_check)
KEY_SEARCH) < 0)
continue;
- /* we've got a match */
- atomic_inc(&keyring->usage);
- read_unlock(&keyring_name_lock);
- goto error;
+ /* we've got a match but we might end up racing with
+ * key_cleanup() if the keyring is currently 'dead'
+ * (ie. it has a zero usage count) */
+ if (!atomic_inc_not_zero(&keyring->usage))
+ continue;
+ goto out;
}
}
- read_unlock(&keyring_name_lock);
keyring = ERR_PTR(-ENOKEY);
-
- error:
+out:
+ read_unlock(&keyring_name_lock);
return keyring;
} /* end find_keyring_by_name() */
@@ -720,8 +724,7 @@ int __key_link(struct key *keyring, struct key *key)
}
/* see if there's a matching key we can displace */
- klist = keyring->payload.subscriptions;
-
+ klist = rcu_dereference_locked_keyring(keyring);
if (klist && klist->nkeys > 0) {
struct key_type *type = key->type;
@@ -765,8 +768,6 @@ int __key_link(struct key *keyring, struct key *key)
if (ret < 0)
goto error2;
- klist = keyring->payload.subscriptions;
-
if (klist && klist->nkeys < klist->maxkeys) {
/* there's sufficient slack space to add directly */
atomic_inc(&key->usage);
@@ -868,7 +869,7 @@ int key_unlink(struct key *keyring, struct key *key)
down_write(&keyring->sem);
- klist = keyring->payload.subscriptions;
+ klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* search the keyring for the key */
for (loop = 0; loop < klist->nkeys; loop++)
@@ -959,7 +960,7 @@ int keyring_clear(struct key *keyring)
/* detach the pointer block with the locks held */
down_write(&keyring->sem);
- klist = keyring->payload.subscriptions;
+ klist = rcu_dereference_locked_keyring(keyring);
if (klist) {
/* adjust the quota */
key_payload_reserve(keyring,
@@ -991,7 +992,9 @@ EXPORT_SYMBOL(keyring_clear);
*/
static void keyring_revoke(struct key *keyring)
{
- struct keyring_list *klist = keyring->payload.subscriptions;
+ struct keyring_list *klist;
+
+ klist = rcu_dereference_locked_keyring(keyring);
/* adjust the quota */
key_payload_reserve(keyring, 0);
@@ -1025,7 +1028,7 @@ void keyring_gc(struct key *keyring, time_t limit)
down_write(&keyring->sem);
- klist = keyring->payload.subscriptions;
+ klist = rcu_dereference_locked_keyring(keyring);
if (!klist)
goto no_klist;