keys: Garbage collect keys for which the domain has been removed

If a key operation domain (such as a network namespace) has been removed
then attempt to garbage collect all the keys that use it.
Signed-off-by: David Howells <dhowells@redhat.com>

include/linux/key.h

@@ -278,6 +278,7 @@ extern void key_revoke(struct key *key);
 extern void key_invalidate(struct key *key);
 extern void key_put(struct key *key);
 extern bool key_put_tag(struct key_tag *tag);
+extern void key_remove_domain(struct key_tag *domain_tag);
 
 static inline struct key *__key_get(struct key *key)
 {
@@ -446,6 +447,7 @@ extern void key_init(void);
 #define key_fsgid_changed(c)		do { } while(0)
 #define key_init()			do { } while(0)
 #define key_free_user_ns(ns)		do { } while(0)
+#define key_remove_domain(d)		do { } while(0)
 
 #endif /* CONFIG_KEYS */
 #endif /* __KERNEL__ */

security/keys/internal.h

@@ -209,7 +209,8 @@ static inline bool key_is_dead(const struct key *key, time64_t limit)
 	return
 		key->flags & ((1 << KEY_FLAG_DEAD) |
 			      (1 << KEY_FLAG_INVALIDATED)) ||
-		(key->expiry > 0 && key->expiry <= limit);
+		(key->expiry > 0 && key->expiry <= limit) ||
+		key->domain_tag->removed;
 }
 
 /*

security/keys/keyring.c

@@ -241,6 +241,21 @@ bool key_put_tag(struct key_tag *tag)
 	return false;
 }
 
+/**
+ * key_remove_domain - Kill off a key domain and gc its keys
+ * @domain_tag: The domain tag to release.
+ *
+ * This marks a domain tag as being dead and releases a ref on it.  If that
+ * wasn't the last reference, the garbage collector is poked to try and delete
+ * all keys that were in the domain.
+ */
+void key_remove_domain(struct key_tag *domain_tag)
+{
+	domain_tag->removed = true;
+	if (!key_put_tag(domain_tag))
+		key_schedule_gc_links();
+}
+
 /*
  * Build the next index key chunk.
  *