KEYS: Add invalidation support
Add support for invalidating a key - which renders it immediately invisible to
further searches and causes the garbage collector to immediately wake up,
remove it from keyrings and then destroy it when it's no longer referenced.
It's better not to do this with keyctl_revoke() as that marks the key to start
returning -EKEYREVOKED to searches when what is actually desired is to have the
key refetched.
To invalidate a key the caller must be granted SEARCH permission by the key.
This may be too strict. It may be better to also permit invalidation if the
caller has any of READ, WRITE or SETATTR permission.
The primary use for this is to evict keys that are cached in special keyrings,
such as the DNS resolver or an ID mapper.
Signed-off-by: David Howells <dhowells@redhat.com>
diff --git a/security/keys/key.c b/security/keys/key.c
index dc62894..c9bf66a 100644
--- a/security/keys/key.c
+++ b/security/keys/key.c
@@ -955,6 +955,28 @@
EXPORT_SYMBOL(key_revoke);
/**
+ * key_invalidate - Invalidate a key.
+ * @key: The key to be invalidated.
+ *
+ * Mark a key as being invalidated and have it cleaned up immediately. The key
+ * is ignored by all searches and other operations from this point.
+ */
+void key_invalidate(struct key *key)
+{
+ kenter("%d", key_serial(key));
+
+ key_check(key);
+
+ if (!test_bit(KEY_FLAG_INVALIDATED, &key->flags)) {
+ down_write_nested(&key->sem, 1);
+ if (!test_and_set_bit(KEY_FLAG_INVALIDATED, &key->flags))
+ key_schedule_gc_links();
+ up_write(&key->sem);
+ }
+}
+EXPORT_SYMBOL(key_invalidate);
+
+/**
* register_key_type - Register a type of key.
* @ktype: The new key type.
*