KEYS: Make request_key() and co fundamentally asynchronous

Make request_key() and co fundamentally asynchronous to make it easier for
NFS to make use of them.  There are now accessor functions that do
asynchronous constructions, a wait function to wait for construction to
complete, and a completion function for the key type to indicate completion
of construction.

Note that the construction queue is now gone.  Instead, keys under
construction are linked in to the appropriate keyring in advance, and that
anyone encountering one must wait for it to be complete before they can use
it.  This is done automatically for userspace.

The following auxiliary changes are also made:

 (1) Key type implementation stuff is split from linux/key.h into
     linux/key-type.h.

 (2) AF_RXRPC provides a way to allocate null rxrpc-type keys so that AFS does
     not need to call key_instantiate_and_link() directly.

 (3) Adjust the debugging macros so that they're -Wformat checked even if
     they are disabled, and make it so they can be enabled simply by defining
     __KDEBUG to be consistent with other code of mine.

 (3) Documentation.

[alan@lxorguk.ukuu.org.uk: keys: missing word in documentation]
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 30 insertions, 3 deletions

diff --git a/net/rxrpc/af_rxrpc.c b/net/rxrpc/af_rxrpc.c
index 0803f305ed08..c680017f5c8e 100644
--- a/net/rxrpc/af_rxrpc.c
+++ b/net/rxrpc/af_rxrpc.c
@@ -14,6 +14,7 @@
 #include <linux/skbuff.h>
 #include <linux/poll.h>
 #include <linux/proc_fs.h>
+#include <linux/key-type.h>
 #include <net/net_namespace.h>
 #include <net/sock.h>
 #include <net/af_rxrpc.h>
diff --git a/net/rxrpc/ar-key.c b/net/rxrpc/ar-key.c
index 7e049ff6ae60..9a8ff684da79 100644
--- a/net/rxrpc/ar-key.c
+++ b/net/rxrpc/ar-key.c
@@ -15,7 +15,7 @@
 #include <linux/module.h>
 #include <linux/net.h>
 #include <linux/skbuff.h>
-#include <linux/key.h>
+#include <linux/key-type.h>
 #include <linux/crypto.h>
 #include <net/sock.h>
 #include <net/af_rxrpc.h>
@@ -40,7 +40,6 @@ struct key_type key_type_rxrpc = {
         .destroy        = rxrpc_destroy,
         .describe       = rxrpc_describe,
 };
-
 EXPORT_SYMBOL(key_type_rxrpc);
 
 /*
@@ -330,5 +329,32 @@ error:
         _leave(" = -ENOMEM [ins %d]", ret);
         return -ENOMEM;
 }
-
 EXPORT_SYMBOL(rxrpc_get_server_data_key);
+
+/**
+ * rxrpc_get_null_key - Generate a null RxRPC key
+ * @keyname: The name to give the key.
+ *
+ * Generate a null RxRPC key that can be used to indicate anonymous security is
+ * required for a particular domain.
+ */
+struct key *rxrpc_get_null_key(const char *keyname)
+{
+        struct key *key;
+        int ret;
+
+        key = key_alloc(&key_type_rxrpc, keyname, 0, 0, current,
+                        KEY_POS_SEARCH, KEY_ALLOC_NOT_IN_QUOTA);
+        if (IS_ERR(key))
+                return key;
+
+        ret = key_instantiate_and_link(key, NULL, 0, NULL, NULL);
+        if (ret < 0) {
+                key_revoke(key);
+                key_put(key);
+                return ERR_PTR(ret);
+        }
+
+        return key;
+}
+EXPORT_SYMBOL(rxrpc_get_null_key);