KEYS: Use RCU dereference wrappers in keyring key type code

The keyring key type code should use RCU dereference wrappers, even when it
holds the keyring's key semaphore.

Reported-by: Vegard Nossum <vegard.nossum@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Acked-by: Serge Hallyn <serue@us.ibm.com>
Signed-off-by: James Morris <jmorris@namei.org>

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 0b27271..1e4b003 100644 (file)
--- 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);
@@ -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;