1 files changed, 85 insertions, 0 deletions

diff --git a/security/keys/keyring.c b/security/keys/keyring.c
index 3dba81c2eba3..ac977f661a79 100644
--- a/security/keys/keyring.c
+++ b/security/keys/keyring.c
@@ -1000,3 +1000,88 @@ static void keyring_revoke(struct key *keyring)
         }
 
 } /* end keyring_revoke() */
+
+/*
+ * Determine whether a key is dead
+ */
+static bool key_is_dead(struct key *key, time_t limit)
+{
+        return test_bit(KEY_FLAG_DEAD, &key->flags) ||
+                (key->expiry > 0 && key->expiry <= limit);
+}
+
+/*
+ * Collect garbage from the contents of a keyring
+ */
+void keyring_gc(struct key *keyring, time_t limit)
+{
+        struct keyring_list *klist, *new;
+        struct key *key;
+        int loop, keep, max;
+
+        kenter("%x", key_serial(keyring));
+
+        down_write(&keyring->sem);
+
+        klist = keyring->payload.subscriptions;
+        if (!klist)
+                goto just_return;
+
+        /* work out how many subscriptions we're keeping */
+        keep = 0;
+        for (loop = klist->nkeys - 1; loop >= 0; loop--)
+                if (!key_is_dead(klist->keys[loop], limit));
+                        keep++;
+
+        if (keep == klist->nkeys)
+                goto just_return;
+
+        /* allocate a new keyring payload */
+        max = roundup(keep, 4);
+        new = kmalloc(sizeof(struct keyring_list) + max * sizeof(struct key *),
+                      GFP_KERNEL);
+        if (!new)
+                goto just_return;
+        new->maxkeys = max;
+        new->nkeys = 0;
+        new->delkey = 0;
+
+        /* install the live keys
+         * - must take care as expired keys may be updated back to life
+         */
+        keep = 0;
+        for (loop = klist->nkeys - 1; loop >= 0; loop--) {
+                key = klist->keys[loop];
+                if (!key_is_dead(key, limit)) {
+                        if (keep >= max)
+                                goto discard_new;
+                        new->keys[keep++] = key_get(key);
+                }
+        }
+        new->nkeys = keep;
+
+        /* adjust the quota */
+        key_payload_reserve(keyring,
+                            sizeof(struct keyring_list) +
+                            KEYQUOTA_LINK_BYTES * keep);
+
+        if (keep == 0) {
+                rcu_assign_pointer(keyring->payload.subscriptions, NULL);
+                kfree(new);
+        } else {
+                rcu_assign_pointer(keyring->payload.subscriptions, new);
+        }
+
+        up_write(&keyring->sem);
+
+        call_rcu(&klist->rcu, keyring_clear_rcu_disposal);
+        kleave(" [yes]");
+        return;
+
+discard_new:
+        new->nkeys = keep;
+        keyring_clear_rcu_disposal(&new->rcu);
+just_return:
+        up_write(&keyring->sem);
+        kleave(" [no]");
+}