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.

[[e-mail]: keys: missing word in documentation]
Signed-off-by: David Howells <[e-mail]>
Signed-off-by: Alan Cox <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

Documentation/keys-request-key.txt

···
 					     const char *callout_string,
 					     void *aux);
 
+or:
+
+	struct key *request_key_async(const struct key_type *type,
+				      const char *description,
+				      const char *callout_string);
+
+or:
+
+	struct key *request_key_async_with_auxdata(const struct key_type *type,
+						   const char *description,
+						   const char *callout_string,
+						   void *aux);
+
 Or by userspace invoking the request_key system call:
 
 	key_serial_t request_key(const char *type,
···
 destroyed.  The kernel interface returns a pointer directly to the key, and
 it's up to the caller to destroy the key.
 
-The request_key_with_auxdata() call is like the in-kernel request_key() call,
-except that it permits auxiliary data to be passed to the upcaller (the default
-is NULL).  This is only useful for those key types that define their own upcall
-mechanism rather than using /sbin/request-key.
+The request_key*_with_auxdata() calls are like the in-kernel request_key*()
+calls, except that they permit auxiliary data to be passed to the upcaller (the
+default is NULL).  This is only useful for those key types that define their
+own upcall mechanism rather than using /sbin/request-key.
+
+The two async in-kernel calls may return keys that are still in the process of
+being constructed.  The two non-async ones will wait for construction to
+complete first.
 
 The userspace interface links the key to a keyring associated with the process
 to prevent the key from going away, and returns the serial number of the key to

Documentation/keys.txt

···
 
 This service allows cryptographic keys, authentication tokens, cross-domain
 user mappings, and similar to be cached in the kernel for the use of
-filesystems other kernel services.
+filesystems and other kernel services.
 
 Keyrings are permitted; these are a special type of key that can hold links to
 other keys. Processes each have three standard keyring subscriptions that a
···
 two different users opening the same file is left to the filesystem author to
 solve.
 
+To access the key manager, the following header must be #included:
+
+	<linux/key.h>
+
+Specific key types should have a header file under include/keys/ that should be
+used to access that type.  For keys of type "user", for example, that would be:
+
+	<keys/user-type.h>
+
 Note that there are two different types of pointers to keys that may be
 encountered:
 
···
 
     This is identical to request_key(), except that the auxiliary data is
     passed to the key_type->request_key() op if it exists.
+
+
+(*) A key can be requested asynchronously by calling one of:
+
+	struct key *request_key_async(const struct key_type *type,
+				      const char *description,
+				      const char *callout_string);
+
+    or:
+
+	struct key *request_key_async_with_auxdata(const struct key_type *type,
+						   const char *description,
+						   const char *callout_string,
+					     	   void *aux);
+
+    which are asynchronous equivalents of request_key() and
+    request_key_with_auxdata() respectively.
+
+    These two functions return with the key potentially still under
+    construction.  To wait for contruction completion, the following should be
+    called:
+
+	int wait_for_key_construction(struct key *key, bool intr);
+
+    The function will wait for the key to finish being constructed and then
+    invokes key_validate() to return an appropriate value to indicate the state
+    of the key (0 indicates the key is usable).
+
+    If intr is true, then the wait can be interrupted by a signal, in which
+    case error ERESTARTSYS will be returned.
 
 
 (*) When it is no longer required, the key should be released using:
···
 
 A kernel service may want to define its own key type. For instance, an AFS
 filesystem might want to define a Kerberos 5 ticket key type. To do this, it
-author fills in a struct key_type and registers it with the system.
+author fills in a key_type struct and registers it with the system.
+
+Source files that implement key types should include the following header file:
+
+	<linux/key-type.h>
 
 The structure has a number of fields, some of which are mandatory:
 
···
      as might happen when the userspace buffer is accessed.
 
 
- (*) int (*request_key)(struct key *key, struct key *authkey, const char *op,
+ (*) int (*request_key)(struct key_construction *cons, const char *op,
 			void *aux);
 
-     This method is optional.  If provided, request_key() and
-     request_key_with_auxdata() will invoke this function rather than
-     upcalling to /sbin/request-key to operate upon a key of this type.
+     This method is optional.  If provided, request_key() and friends will
+     invoke this function rather than upcalling to /sbin/request-key to operate
+     upon a key of this type.
 
-     The aux parameter is as passed to request_key_with_auxdata() or is NULL
-     otherwise.  Also passed are the key to be operated upon, the
-     authorisation key for this operation and the operation type (currently
-     only "create").
+     The aux parameter is as passed to request_key_async_with_auxdata() and
+     similar or is NULL otherwise.  Also passed are the construction record for
+     the key to be operated upon and the operation type (currently only
+     "create").
 
-     This function should return only when the upcall is complete.  Upon return
-     the authorisation key will be revoked, and the target key will be
-     negatively instantiated if it is still uninstantiated.  The error will be
-     returned to the caller of request_key*().
+     This method is permitted to return before the upcall is complete, but the
+     following function must be called under all circumstances to complete the
+     instantiation process, whether or not it succeeds, whether or not there's
+     an error:
+
+	void complete_request_key(struct key_construction *cons, int error);
+
+     The error parameter should be 0 on success, -ve on error.  The
+     construction record is destroyed by this action and the authorisation key
+     will be revoked.  If an error is indicated, the key under construction
+     will be negatively instantiated if it wasn't already instantiated.
+
+     If this method returns an error, that error will be returned to the
+     caller of request_key*().  complete_request_key() must be called prior to
+     returning.
+
+     The key under construction and the authorisation key can be found in the
+     key_construction struct pointed to by cons:
+
+     (*) struct key *key;
+
+     	 The key under construction.
+
+     (*) struct key *authkey;
+
+     	 The authorisation key.
 
 
 ============================

Documentation/networking/rxrpc.txt

···
 
      This is used to extract the error number from a message indicating either
      a local error occurred or a network error occurred.
+
+ (*) Allocate a null key for doing anonymous security.
+
+	struct key *rxrpc_get_null_key(const char *keyname);
+
+     This is used to allocate a null RxRPC key that can be used to indicate
+     anonymous security for a particular domain.

fs/afs/cell.c

···
 static struct afs_cell *afs_cell_alloc(const char *name, char *vllist)
 {
 	struct afs_cell *cell;
+	struct key *key;
 	size_t namelen;
 	char keyname[4 + AFS_MAXCELLNAME + 1], *cp, *dp, *next;
 	int ret;
···
 	do {
 		*dp++ = toupper(*cp);
 	} while (*cp++);
-	cell->anonymous_key = key_alloc(&key_type_rxrpc, keyname, 0, 0, current,
-					KEY_POS_SEARCH, KEY_ALLOC_NOT_IN_QUOTA);
-	if (IS_ERR(cell->anonymous_key)) {
-		_debug("no key");
-		ret = PTR_ERR(cell->anonymous_key);
-		goto error;
-	}
 
-	ret = key_instantiate_and_link(cell->anonymous_key, NULL, 0,
-				       NULL, NULL);
-	if (ret < 0) {
-		_debug("instantiate failed");
+	key = rxrpc_get_null_key(keyname);
+	if (IS_ERR(key)) {
+		_debug("no key");
+		ret = PTR_ERR(key);
 		goto error;
 	}
+	cell->anonymous_key = key;
 
 	_debug("anon key %p{%x}",
 	       cell->anonymous_key, key_serial(cell->anonymous_key));

include/keys/rxrpc-type.h

···
  */
 extern struct key_type key_type_rxrpc;
 
+extern struct key *rxrpc_get_null_key(const char *);
+
 #endif /* _KEYS_USER_TYPE_H */

include/linux/key-type.h

···
+/* Definitions for key type implementations
+ *
+ * Copyright (C) 2007 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells ([e-mail])
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#ifndef _LINUX_KEY_TYPE_H
+#define _LINUX_KEY_TYPE_H
+
+#include <linux/key.h>
+
+#ifdef CONFIG_KEYS
+
+/*
+ * key under-construction record
+ * - passed to the request_key actor if supplied
+ */
+struct key_construction {
+	struct key	*key;	/* key being constructed */
+	struct key	*authkey;/* authorisation for key being constructed */
+};
+
+typedef int (*request_key_actor_t)(struct key_construction *key,
+				   const char *op, void *aux);
+
+/*
+ * kernel managed key type definition
+ */
+struct key_type {
+	/* name of the type */
+	const char *name;
+
+	/* default payload length for quota precalculation (optional)
+	 * - this can be used instead of calling key_payload_reserve(), that
+	 *   function only needs to be called if the real datalen is different
+	 */
+	size_t def_datalen;
+
+	/* instantiate a key of this type
+	 * - this method should call key_payload_reserve() to determine if the
+	 *   user's quota will hold the payload
+	 */
+	int (*instantiate)(struct key *key, const void *data, size_t datalen);
+
+	/* update a key of this type (optional)
+	 * - this method should call key_payload_reserve() to recalculate the
+	 *   quota consumption
+	 * - the key must be locked against read when modifying
+	 */
+	int (*update)(struct key *key, const void *data, size_t datalen);
+
+	/* match a key against a description */
+	int (*match)(const struct key *key, const void *desc);
+
+	/* clear some of the data from a key on revokation (optional)
+	 * - the key's semaphore will be write-locked by the caller
+	 */
+	void (*revoke)(struct key *key);
+
+	/* clear the data from a key (optional) */
+	void (*destroy)(struct key *key);
+
+	/* describe a key */
+	void (*describe)(const struct key *key, struct seq_file *p);
+
+	/* read a key's data (optional)
+	 * - permission checks will be done by the caller
+	 * - the key's semaphore will be readlocked by the caller
+	 * - should return the amount of data that could be read, no matter how
+	 *   much is copied into the buffer
+	 * - shouldn't do the copy if the buffer is NULL
+	 */
+	long (*read)(const struct key *key, char __user *buffer, size_t buflen);
+
+	/* handle request_key() for this type instead of invoking
+	 * /sbin/request-key (optional)
+	 * - key is the key to instantiate
+	 * - authkey is the authority to assume when instantiating this key
+	 * - op is the operation to be done, usually "create"
+	 * - the call must not return until the instantiation process has run
+	 *   its course
+	 */
+	request_key_actor_t request_key;
+
+	/* internal fields */
+	struct list_head	link;		/* link in types list */
+};
+
+extern struct key_type key_type_keyring;
+
+extern int register_key_type(struct key_type *ktype);
+extern void unregister_key_type(struct key_type *ktype);
+
+extern int key_payload_reserve(struct key *key, size_t datalen);
+extern int key_instantiate_and_link(struct key *key,
+				    const void *data,
+				    size_t datalen,
+				    struct key *keyring,
+				    struct key *instkey);
+extern int key_negate_and_link(struct key *key,
+			       unsigned timeout,
+			       struct key *keyring,
+			       struct key *instkey);
+extern void complete_request_key(struct key_construction *cons, int error);
+
+#endif /* CONFIG_KEYS */
+#endif /* _LINUX_KEY_TYPE_H */

include/linux/key.h

···
-/* key.h: authentication token and access key management
+/* Authentication token and access key management
  *
- * Copyright (C) 2004 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004, 2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells ([e-mail])
  *
  * This program is free software; you can redistribute it and/or
···
 	} payload;
 };
 
-/*****************************************************************************/
-/*
- * kernel managed key type definition
- */
-typedef int (*request_key_actor_t)(struct key *key, struct key *authkey,
-				   const char *op, void *aux);
-
-struct key_type {
-	/* name of the type */
-	const char *name;
-
-	/* default payload length for quota precalculation (optional)
-	 * - this can be used instead of calling key_payload_reserve(), that
-	 *   function only needs to be called if the real datalen is different
-	 */
-	size_t def_datalen;
-
-	/* instantiate a key of this type
-	 * - this method should call key_payload_reserve() to determine if the
-	 *   user's quota will hold the payload
-	 */
-	int (*instantiate)(struct key *key, const void *data, size_t datalen);
-
-	/* update a key of this type (optional)
-	 * - this method should call key_payload_reserve() to recalculate the
-	 *   quota consumption
-	 * - the key must be locked against read when modifying
-	 */
-	int (*update)(struct key *key, const void *data, size_t datalen);
-
-	/* match a key against a description */
-	int (*match)(const struct key *key, const void *desc);
-
-	/* clear some of the data from a key on revokation (optional)
-	 * - the key's semaphore will be write-locked by the caller
-	 */
-	void (*revoke)(struct key *key);
-
-	/* clear the data from a key (optional) */
-	void (*destroy)(struct key *key);
-
-	/* describe a key */
-	void (*describe)(const struct key *key, struct seq_file *p);
-
-	/* read a key's data (optional)
-	 * - permission checks will be done by the caller
-	 * - the key's semaphore will be readlocked by the caller
-	 * - should return the amount of data that could be read, no matter how
-	 *   much is copied into the buffer
-	 * - shouldn't do the copy if the buffer is NULL
-	 */
-	long (*read)(const struct key *key, char __user *buffer, size_t buflen);
-
-	/* handle request_key() for this type instead of invoking
-	 * /sbin/request-key (optional)
-	 * - key is the key to instantiate
-	 * - authkey is the authority to assume when instantiating this key
-	 * - op is the operation to be done, usually "create"
-	 * - the call must not return until the instantiation process has run
-	 *   its course
-	 */
-	request_key_actor_t request_key;
-
-	/* internal fields */
-	struct list_head	link;		/* link in types list */
-};
-
-extern struct key_type key_type_keyring;
-
-extern int register_key_type(struct key_type *ktype);
-extern void unregister_key_type(struct key_type *ktype);
-
 extern struct key *key_alloc(struct key_type *type,
 			     const char *desc,
 			     uid_t uid, gid_t gid,
···
 #define KEY_ALLOC_QUOTA_OVERRUN	0x0001	/* add to quota, permit even if overrun */
 #define KEY_ALLOC_NOT_IN_QUOTA	0x0002	/* not in quota */
 
-extern int key_payload_reserve(struct key *key, size_t datalen);
-extern int key_instantiate_and_link(struct key *key,
-				    const void *data,
-				    size_t datalen,
-				    struct key *keyring,
-				    struct key *instkey);
-extern int key_negate_and_link(struct key *key,
-			       unsigned timeout,
-			       struct key *keyring,
-			       struct key *instkey);
 extern void key_revoke(struct key *key);
 extern void key_put(struct key *key);
 
···
 					    const char *description,
 					    const char *callout_info,
 					    void *aux);
+
+extern struct key *request_key_async(struct key_type *type,
+				     const char *description,
+				     const char *callout_info);
+
+extern struct key *request_key_async_with_auxdata(struct key_type *type,
+						  const char *description,
+						  const char *callout_info,
+						  void *aux);
+
+extern int wait_for_key_construction(struct key *key, bool intr);
 
 extern int key_validate(struct key *key);
 
···
 			   struct key *key);
 
 extern struct key *key_lookup(key_serial_t id);
-
-extern void keyring_replace_payload(struct key *key, void *replacement);
 
 #define key_serial(key) ((key) ? (key)->serial : 0)
 

net/rxrpc/af_rxrpc.c

···
 #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>

net/rxrpc/ar-key.c

···
 #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>
···
 	.destroy	= rxrpc_destroy,
 	.describe	= rxrpc_describe,
 };
-
 EXPORT_SYMBOL(key_type_rxrpc);
 
 /*
···
 	_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);

security/keys/internal.h

···
 /* internal.h: authentication token and access key management internal defs
  *
- * Copyright (C) 2003-5 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2003-5, 2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells ([e-mail])
  *
  * This program is free software; you can redistribute it and/or
···
 #ifndef _INTERNAL_H
 #define _INTERNAL_H
 
-#include <linux/key.h>
+#include <linux/key-type.h>
 #include <linux/key-ui.h>
 
-#if 0
-#define kenter(FMT, a...)	printk("==> %s("FMT")\n",__FUNCTION__ , ## a)
-#define kleave(FMT, a...)	printk("<== %s()"FMT"\n",__FUNCTION__ , ## a)
-#define kdebug(FMT, a...)	printk(FMT"\n" , ## a)
+static inline __attribute__((format(printf, 1, 2)))
+void no_printk(const char *fmt, ...)
+{
+}
+
+#ifdef __KDEBUG
+#define kenter(FMT, ...) \
+	printk(KERN_DEBUG "==> %s("FMT")\n", __FUNCTION__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+	printk(KERN_DEBUG "<== %s()"FMT"\n", __FUNCTION__, ##__VA_ARGS__)
+#define kdebug(FMT, ...) \
+	printk(KERN_DEBUG "xxx" FMT"yyy\n", ##__VA_ARGS__)
 #else
-#define kenter(FMT, a...)	do {} while(0)
-#define kleave(FMT, a...)	do {} while(0)
-#define kdebug(FMT, a...)	do {} while(0)
+#define kenter(FMT, ...) \
+	no_printk(KERN_DEBUG "==> %s("FMT")\n", __FUNCTION__, ##__VA_ARGS__)
+#define kleave(FMT, ...) \
+	no_printk(KERN_DEBUG "<== %s()"FMT"\n", __FUNCTION__, ##__VA_ARGS__)
+#define kdebug(FMT, ...) \
+	no_printk(KERN_DEBUG FMT"\n", ##__VA_ARGS__)
 #endif
 
 extern struct key_type key_type_user;
···
  */
 struct key_user {
 	struct rb_node		node;
-	struct list_head	consq;		/* construction queue */
+	struct mutex		cons_lock;	/* construction initiation lock */
 	spinlock_t		lock;
 	atomic_t		usage;		/* for accessing qnkeys & qnbytes */
 	atomic_t		nkeys;		/* number of keys */
···
 extern struct rb_root key_serial_tree;
 extern spinlock_t key_serial_lock;
 extern struct semaphore key_alloc_sem;
-extern struct rw_semaphore key_construction_sem;
+extern struct mutex key_construction_mutex;
 extern wait_queue_head_t request_key_conswq;
 
 
···
 struct request_key_auth {
 	struct key		*target_key;
 	struct task_struct	*context;
-	const char		*callout_info;
+	char			*callout_info;
 	pid_t			pid;
 };
 

security/keys/key.c

···
-/* key.c: basic authentication token and access key management
+/* Basic authentication token and access key management
  *
- * Copyright (C) 2004-6 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells ([e-mail])
  *
  * This program is free software; you can redistribute it and/or
···
 static DECLARE_WORK(key_cleanup_task, key_cleanup);
 
 /* we serialise key instantiation and link */
-DECLARE_RWSEM(key_construction_sem);
+DEFINE_MUTEX(key_construction_mutex);
 
 /* any key who's type gets unegistered will be re-typed to this */
 static struct key_type key_type_dead = {
···
 	candidate->qnkeys = 0;
 	candidate->qnbytes = 0;
 	spin_lock_init(&candidate->lock);
-	INIT_LIST_HEAD(&candidate->consq);
+	mutex_init(&candidate->cons_lock);
 
 	rb_link_node(&candidate->node, parent, p);
 	rb_insert_color(&candidate->node, &key_user_tree);
···
 	awaken = 0;
 	ret = -EBUSY;
 
-	down_write(&key_construction_sem);
+	mutex_lock(&key_construction_mutex);
 
 	/* can't instantiate twice */
 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
···
 		}
 	}
 
-	up_write(&key_construction_sem);
+	mutex_unlock(&key_construction_mutex);
 
 	/* wake up anyone waiting for a key to be constructed */
 	if (awaken)
-		wake_up_all(&request_key_conswq);
+		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 
 	return ret;
 
···
 	if (keyring)
 		down_write(&keyring->sem);
 
-	down_write(&key_construction_sem);
+	mutex_lock(&key_construction_mutex);
 
 	/* can't instantiate twice */
 	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
···
 			key_revoke(instkey);
 	}
 
-	up_write(&key_construction_sem);
+	mutex_unlock(&key_construction_mutex);
 
 	if (keyring)
 		up_write(&keyring->sem);
 
 	/* wake up anyone waiting for a key to be constructed */
 	if (awaken)
-		wake_up_all(&request_key_conswq);
+		wake_up_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT);
 
 	return ret;
 
···
 {
 	key_check(key);
 
-	/* make sure no one's trying to change or use the key when we mark
-	 * it */
-	down_write(&key->sem);
-	set_bit(KEY_FLAG_REVOKED, &key->flags);
-
-	if (key->type->revoke)
+	/* make sure no one's trying to change or use the key when we mark it
+	 * - we tell lockdep that we might nest because we might be revoking an
+	 *   authorisation key whilst holding the sem on a key we've just
+	 *   instantiated
+	 */
+	down_write_nested(&key->sem, 1);
+	if (!test_and_set_bit(KEY_FLAG_REVOKED, &key->flags) &&
+	    key->type->revoke)
 		key->type->revoke(key);
 
 	up_write(&key->sem);

security/keys/process_keys.c

···
 /* the root user's tracking struct */
 struct key_user root_key_user = {
 	.usage		= ATOMIC_INIT(3),
-	.consq		= LIST_HEAD_INIT(root_key_user.consq),
+	.cons_lock	= __MUTEX_INITIALIZER(root_key_user.cons_lock),
 	.lock		= __SPIN_LOCK_UNLOCKED(root_key_user.lock),
 	.nkeys		= ATOMIC_INIT(2),
 	.nikeys		= ATOMIC_INIT(2),
···
 		break;
 	}
 
-	/* check the status */
-	if (perm) {
+	if (!partial) {
+		ret = wait_for_key_construction(key, true);
+		switch (ret) {
+		case -ERESTARTSYS:
+			goto invalid_key;
+		default:
+			if (perm)
+				goto invalid_key;
+		case 0:
+			break;
+		}
+	} else if (perm) {
 		ret = key_validate(key);
 		if (ret < 0)
 			goto invalid_key;

security/keys/request_key.c

···
-/* request_key.c: request a key from userspace
+/* Request a key from userspace
  *
- * Copyright (C) 2004-6 Red Hat, Inc. All Rights Reserved.
+ * Copyright (C) 2004-2007 Red Hat, Inc. All Rights Reserved.
  * Written by David Howells ([e-mail])
  *
  * This program is free software; you can redistribute it and/or
···
 #include <linux/keyctl.h>
 #include "internal.h"
 
-struct key_construction {
-	struct list_head	link;	/* link in construction queue */
-	struct key		*key;	/* key being constructed */
-};
+/*
+ * wait_on_bit() sleep function for uninterruptible waiting
+ */
+static int key_wait_bit(void *flags)
+{
+	schedule();
+	return 0;
+}
 
-/* when waiting for someone else's keys, you get added to this */
-DECLARE_WAIT_QUEUE_HEAD(request_key_conswq);
+/*
+ * wait_on_bit() sleep function for interruptible waiting
+ */
+static int key_wait_bit_intr(void *flags)
+{
+	schedule();
+	return signal_pending(current) ? -ERESTARTSYS : 0;
+}
 
-/*****************************************************************************/
+/*
+ * call to complete the construction of a key
+ */
+void complete_request_key(struct key_construction *cons, int error)
+{
+	kenter("{%d,%d},%d", cons->key->serial, cons->authkey->serial, error);
+
+	if (error < 0)
+		key_negate_and_link(cons->key, key_negative_timeout, NULL,
+				    cons->authkey);
+	else
+		key_revoke(cons->authkey);
+
+	key_put(cons->key);
+	key_put(cons->authkey);
+	kfree(cons);
+}
+EXPORT_SYMBOL(complete_request_key);
+
 /*
  * request userspace finish the construction of a key
  * - execute "/sbin/request-key <op> <key> <uid> <gid> <keyring> <keyring> <keyring>"
  */
-static int call_sbin_request_key(struct key *key,
-				 struct key *authkey,
+static int call_sbin_request_key(struct key_construction *cons,
 				 const char *op,
 				 void *aux)
 {
 	struct task_struct *tsk = current;
 	key_serial_t prkey, sskey;
-	struct key *keyring;
+	struct key *key = cons->key, *authkey = cons->authkey, *keyring;
 	char *argv[9], *envp[3], uid_str[12], gid_str[12];
 	char key_str[12], keyring_str[3][12];
 	char desc[20];
···
 		rcu_read_lock();
 		sskey = rcu_dereference(tsk->signal->session_keyring)->serial;
 		rcu_read_unlock();
-	}
-	else {
+	} else {
 		sskey = tsk->user->session_keyring->serial;
 	}
 
···
 	/* do it */
 	ret = call_usermodehelper_keys(argv[0], argv, envp, keyring,
 				       UMH_WAIT_PROC);
+	kdebug("usermode -> 0x%x", ret);
+	if (ret >= 0) {
+		/* ret is the exit/wait code */
+		if (test_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags) ||
+		    key_validate(key) < 0)
+			ret = -ENOKEY;
+		else
+			/* ignore any errors from userspace if the key was
+			 * instantiated */
+			ret = 0;
+	}
 
 error_link:
 	key_put(keyring);
 
 error_alloc:
 	kleave(" = %d", ret);
+	complete_request_key(cons, ret);
 	return ret;
+}
 
-} /* end call_sbin_request_key() */
-
-/*****************************************************************************/
 /*
- * call out to userspace for the key
- * - called with the construction sem held, but the sem is dropped here
+ * call out to userspace for key construction
  * - we ignore program failure and go on key status instead
  */
-static struct key *__request_key_construction(struct key_type *type,
-					      const char *description,
-					      const char *callout_info,
-					      void *aux,
-					      unsigned long flags)
+static int construct_key(struct key *key, const char *callout_info, void *aux)
 {
+	struct key_construction *cons;
 	request_key_actor_t actor;
-	struct key_construction cons;
-	struct timespec now;
-	struct key *key, *authkey;
-	int ret, negated;
+	struct key *authkey;
+	int ret;
 
-	kenter("%s,%s,%s,%lx", type->name, description, callout_info, flags);
+	kenter("%d,%s,%p", key->serial, callout_info, aux);
 
-	/* create a key and add it to the queue */
-	key = key_alloc(type, description,
-			current->fsuid, current->fsgid, current, KEY_POS_ALL,
-			flags);
-	if (IS_ERR(key))
-		goto alloc_failed;
-
-	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
-
-	cons.key = key;
-	list_add_tail(&cons.link, &key->user->consq);
-
-	/* we drop the construction sem here on behalf of the caller */
-	up_write(&key_construction_sem);
+	cons = kmalloc(sizeof(*cons), GFP_KERNEL);
+	if (!cons)
+		return -ENOMEM;
 
 	/* allocate an authorisation key */
 	authkey = request_key_auth_new(key, callout_info);
 	if (IS_ERR(authkey)) {
+		kfree(cons);
 		ret = PTR_ERR(authkey);
 		authkey = NULL;
-		goto alloc_authkey_failed;
+	} else {
+		cons->authkey = key_get(authkey);
+		cons->key = key_get(key);
+
+		/* make the call */
+		actor = call_sbin_request_key;
+		if (key->type->request_key)
+			actor = key->type->request_key;
+
+		ret = actor(cons, "create", aux);
+
+		/* check that the actor called complete_request_key() prior to
+		 * returning an error */
+		WARN_ON(ret < 0 &&
+			!test_bit(KEY_FLAG_REVOKED, &authkey->flags));
+		key_put(authkey);
 	}
 
-	/* make the call */
-	actor = call_sbin_request_key;
-	if (type->request_key)
-		actor = type->request_key;
-	ret = actor(key, authkey, "create", aux);
-	if (ret < 0)
-		goto request_failed;
+	kleave(" = %d", ret);
+	return ret;
+}
 
-	/* if the key wasn't instantiated, then we want to give an error */
-	ret = -ENOKEY;
-	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags))
-		goto request_failed;
-
-	key_revoke(authkey);
-	key_put(authkey);
-
-	down_write(&key_construction_sem);
-	list_del(&cons.link);
-	up_write(&key_construction_sem);
-
-	/* also give an error if the key was negatively instantiated */
-check_not_negative:
-	if (test_bit(KEY_FLAG_NEGATIVE, &key->flags)) {
-		key_put(key);
-		key = ERR_PTR(-ENOKEY);
-	}
-
-out:
-	kleave(" = %p", key);
-	return key;
-
-request_failed:
-	key_revoke(authkey);
-	key_put(authkey);
-
-alloc_authkey_failed:
-	/* it wasn't instantiated
-	 * - remove from construction queue
-	 * - mark the key as dead
-	 */
-	negated = 0;
-	down_write(&key_construction_sem);
-
-	list_del(&cons.link);
-
-	/* check it didn't get instantiated between the check and the down */
-	if (!test_bit(KEY_FLAG_INSTANTIATED, &key->flags)) {
-		set_bit(KEY_FLAG_NEGATIVE, &key->flags);
-		set_bit(KEY_FLAG_INSTANTIATED, &key->flags);
-		negated = 1;
-	}
-
-	clear_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
-
-	up_write(&key_construction_sem);
-
-	if (!negated)
-		goto check_not_negative; /* surprisingly, the key got
-					  * instantiated */
-
-	/* set the timeout and store in the session keyring if we can */
-	now = current_kernel_time();
-	key->expiry = now.tv_sec + key_negative_timeout;
-
-	if (current->signal->session_keyring) {
-		struct key *keyring;
-
-		rcu_read_lock();
-		keyring = rcu_dereference(current->signal->session_keyring);
-		atomic_inc(&keyring->usage);
-		rcu_read_unlock();
-
-		key_link(keyring, key);
-		key_put(keyring);
-	}
-
-	key_put(key);
-
-	/* notify anyone who was waiting */
-	wake_up_all(&request_key_conswq);
-
-	key = ERR_PTR(ret);
-	goto out;
-
-alloc_failed:
-	up_write(&key_construction_sem);
-	goto out;
-
-} /* end __request_key_construction() */
-
-/*****************************************************************************/
 /*
- * call out to userspace to request the key
- * - we check the construction queue first to see if an appropriate key is
- *   already being constructed by userspace
+ * link a key to the appropriate destination keyring
+ * - the caller must hold a write lock on the destination keyring
  */
-static struct key *request_key_construction(struct key_type *type,
-					    const char *description,
-					    const char *callout_info,
-					    void *aux,
-					    struct key_user *user,
-					    unsigned long flags)
-{
-	struct key_construction *pcons;
-	struct key *key, *ckey;
-
-	DECLARE_WAITQUEUE(myself, current);
-
-	kenter("%s,%s,{%d},%s,%lx",
-	       type->name, description, user->uid, callout_info, flags);
-
-	/* see if there's such a key under construction already */
-	down_write(&key_construction_sem);
-
-	list_for_each_entry(pcons, &user->consq, link) {
-		ckey = pcons->key;
-
-		if (ckey->type != type)
-			continue;
-
-		if (type->match(ckey, description))
-			goto found_key_under_construction;
-	}
-
-	/* see about getting userspace to construct the key */
-	key = __request_key_construction(type, description, callout_info, aux,
-					 flags);
- error:
-	kleave(" = %p", key);
-	return key;
-
-	/* someone else has the same key under construction
-	 * - we want to keep an eye on their key
-	 */
- found_key_under_construction:
-	atomic_inc(&ckey->usage);
-	up_write(&key_construction_sem);
-
-	/* wait for the key to be completed one way or another */
-	add_wait_queue(&request_key_conswq, &myself);
-
-	for (;;) {
-		set_current_state(TASK_INTERRUPTIBLE);
-		if (!test_bit(KEY_FLAG_USER_CONSTRUCT, &ckey->flags))
-			break;
-		if (signal_pending(current))
-			break;
-		schedule();
-	}
-
-	set_current_state(TASK_RUNNING);
-	remove_wait_queue(&request_key_conswq, &myself);
-
-	/* we'll need to search this process's keyrings to see if the key is
-	 * now there since we can't automatically assume it's also available
-	 * there */
-	key_put(ckey);
-	ckey = NULL;
-
-	key = NULL; /* request a retry */
-	goto error;
-
-} /* end request_key_construction() */
-
-/*****************************************************************************/
-/*
- * link a freshly minted key to an appropriate destination keyring
- */
-static void request_key_link(struct key *key, struct key *dest_keyring)
+static void construct_key_make_link(struct key *key, struct key *dest_keyring)
 {
 	struct task_struct *tsk = current;
 	struct key *drop = NULL;
···
 				break;
 
 		case KEY_REQKEY_DEFL_USER_SESSION_KEYRING:
-			dest_keyring = current->user->session_keyring;
+			dest_keyring = tsk->user->session_keyring;
 			break;
 
 		case KEY_REQKEY_DEFL_USER_KEYRING:
-			dest_keyring = current->user->uid_keyring;
+			dest_keyring = tsk->user->uid_keyring;
 			break;
 
 		case KEY_REQKEY_DEFL_GROUP_KEYRING:
···
 	}
 
 	/* and attach the key to it */
-	key_link(dest_keyring, key);
-
+	__key_link(dest_keyring, key);
 	key_put(drop);
-
 	kleave("");
+}
 
-} /* end request_key_link() */
+/*
+ * allocate a new key in under-construction state and attempt to link it in to
+ * the requested place
+ * - may return a key that's already under construction instead
+ */
+static int construct_alloc_key(struct key_type *type,
+			       const char *description,
+			       struct key *dest_keyring,
+			       unsigned long flags,
+			       struct key_user *user,
+			       struct key **_key)
+{
+	struct key *key;
+	key_ref_t key_ref;
 
-/*****************************************************************************/
+	kenter("%s,%s,,,", type->name, description);
+
+	mutex_lock(&user->cons_lock);
+
+	key = key_alloc(type, description,
+			current->fsuid, current->fsgid, current, KEY_POS_ALL,
+			flags);
+	if (IS_ERR(key))
+		goto alloc_failed;
+
+	set_bit(KEY_FLAG_USER_CONSTRUCT, &key->flags);
+
+	if (dest_keyring)
+		down_write(&dest_keyring->sem);
+
+	/* attach the key to the destination keyring under lock, but we do need
+	 * to do another check just in case someone beat us to it whilst we
+	 * waited for locks */
+	mutex_lock(&key_construction_mutex);
+
+	key_ref = search_process_keyrings(type, description, type->match,
+					  current);
+	if (!IS_ERR(key_ref))
+		goto key_already_present;
+
+	if (dest_keyring)
+		construct_key_make_link(key, dest_keyring);
+
+	mutex_unlock(&key_construction_mutex);
+	if (dest_keyring)
+		up_write(&dest_keyring->sem);
+	mutex_unlock(&user->cons_lock);
+	*_key = key;
+	kleave(" = 0 [%d]", key_serial(key));
+	return 0;
+
+key_already_present:
+	mutex_unlock(&key_construction_mutex);
+	if (dest_keyring)
+		up_write(&dest_keyring->sem);
+	mutex_unlock(&user->cons_lock);
+	key_put(key);
+	*_key = key = key_ref_to_ptr(key_ref);
+	kleave(" = -EINPROGRESS [%d]", key_serial(key));
+	return -EINPROGRESS;
+
+alloc_failed:
+	mutex_unlock(&user->cons_lock);
+	*_key = NULL;
+	kleave(" = %ld", PTR_ERR(key));
+	return PTR_ERR(key);
+}
+
+/*
+ * commence key construction
+ */
+static struct key *construct_key_and_link(struct key_type *type,
+					  const char *description,
+					  const char *callout_info,
+					  void *aux,
+					  struct key *dest_keyring,
+					  unsigned long flags)
+{
+	struct key_user *user;
+	struct key *key;
+	int ret;
+
+	user = key_user_lookup(current->fsuid);
+	if (!user)
+		return ERR_PTR(-ENOMEM);
+
+	ret = construct_alloc_key(type, description, dest_keyring, flags, user,
+				  &key);
+	key_user_put(user);
+
+	if (ret == 0) {
+		ret = construct_key(key, callout_info, aux);
+		if (ret < 0)
+			goto construction_failed;
+	}
+
+	return key;
+
+construction_failed:
+	key_negate_and_link(key, key_negative_timeout, NULL, NULL);
+	key_put(key);
+	return ERR_PTR(ret);
+}
+
 /*
  * request a key
  * - search the process's keyrings
···
 				 struct key *dest_keyring,
 				 unsigned long flags)
 {
-	struct key_user *user;
 	struct key *key;
 	key_ref_t key_ref;
 
···
 	key_ref = search_process_keyrings(type, description, type->match,
 					  current);
 
-	kdebug("search 1: %p", key_ref);
-
 	if (!IS_ERR(key_ref)) {
 		key = key_ref_to_ptr(key_ref);
-	}
-	else if (PTR_ERR(key_ref) != -EAGAIN) {
+	} else if (PTR_ERR(key_ref) != -EAGAIN) {
 		key = ERR_PTR(PTR_ERR(key_ref));
-	}
-	else  {
+	} else  {
 		/* the search failed, but the keyrings were searchable, so we
 		 * should consult userspace if we can */
 		key = ERR_PTR(-ENOKEY);
 		if (!callout_info)
 			goto error;
 
-		/* - get hold of the user's construction queue */
-		user = key_user_lookup(current->fsuid);
-		if (!user)
-			goto nomem;
-
-		for (;;) {
-			if (signal_pending(current))
-				goto interrupted;
-
-			/* ask userspace (returns NULL if it waited on a key
-			 * being constructed) */
-			key = request_key_construction(type, description,
-						       callout_info, aux,
-						       user, flags);
-			if (key)
-				break;
-
-			/* someone else made the key we want, so we need to
-			 * search again as it might now be available to us */
-			key_ref = search_process_keyrings(type, description,
-							  type->match,
-							  current);
-
-			kdebug("search 2: %p", key_ref);
-
-			if (!IS_ERR(key_ref)) {
-				key = key_ref_to_ptr(key_ref);
-				break;
-			}
-
-			if (PTR_ERR(key_ref) != -EAGAIN) {
-				key = ERR_PTR(PTR_ERR(key_ref));
-				break;
-			}
-		}
-
-		key_user_put(user);
-
-		/* link the new key into the appropriate keyring */
-		if (!IS_ERR(key))
-			request_key_link(key, dest_keyring);
+		key = construct_key_and_link(type, description, callout_info,
+					     aux, dest_keyring, flags);
 	}
 
 error:
 	kleave(" = %p", key);
 	return key;
+}
 
-nomem:
-	key = ERR_PTR(-ENOMEM);
-	goto error;
+/*
+ * wait for construction of a key to complete
+ */
+int wait_for_key_construction(struct key *key, bool intr)
+{
+	int ret;
 
-interrupted:
-	key_user_put(user);
-	key = ERR_PTR(-EINTR);
-	goto error;
+	ret = wait_on_bit(&key->flags, KEY_FLAG_USER_CONSTRUCT,
+			  intr ? key_wait_bit_intr : key_wait_bit,
+			  intr ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE);
+	if (ret < 0)
+		return ret;
+	return key_validate(key);
+}
+EXPORT_SYMBOL(wait_for_key_construction);
 
-} /* end request_key_and_link() */
-
-/*****************************************************************************/
 /*
  * request a key
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
+ * - waits uninterruptible for creation to complete
  */
 struct key *request_key(struct key_type *type,
 			const char *description,
 			const char *callout_info)
 {
-	return request_key_and_link(type, description, callout_info, NULL,
-				    NULL, KEY_ALLOC_IN_QUOTA);
+	struct key *key;
+	int ret;
 
-} /* end request_key() */
-
+	key = request_key_and_link(type, description, callout_info, NULL,
+				   NULL, KEY_ALLOC_IN_QUOTA);
+	if (!IS_ERR(key)) {
+		ret = wait_for_key_construction(key, false);
+		if (ret < 0) {
+			key_put(key);
+			return ERR_PTR(ret);
+		}
+	}
+	return key;
+}
 EXPORT_SYMBOL(request_key);
 
-/*****************************************************************************/
 /*
  * request a key with auxiliary data for the upcaller
  * - search the process's keyrings
  * - check the list of keys being created or updated
  * - call out to userspace for a key if supplementary info was provided
+ * - waits uninterruptible for creation to complete
  */
 struct key *request_key_with_auxdata(struct key_type *type,
 				     const char *description,
 				     const char *callout_info,
 				     void *aux)
 {
+	struct key *key;
+	int ret;
+
+	key = request_key_and_link(type, description, callout_info, aux,
+				   NULL, KEY_ALLOC_IN_QUOTA);
+	if (!IS_ERR(key)) {
+		ret = wait_for_key_construction(key, false);
+		if (ret < 0) {
+			key_put(key);
+			return ERR_PTR(ret);
+		}
+	}
+	return key;
+}
+EXPORT_SYMBOL(request_key_with_auxdata);
+
+/*
+ * request a key (allow async construction)
+ * - search the process's keyrings
+ * - check the list of keys being created or updated
+ * - call out to userspace for a key if supplementary info was provided
+ */
+struct key *request_key_async(struct key_type *type,
+			      const char *description,
+			      const char *callout_info)
+{
+	return request_key_and_link(type, description, callout_info, NULL,
+				    NULL, KEY_ALLOC_IN_QUOTA);
+}
+EXPORT_SYMBOL(request_key_async);
+
+/*
+ * request a key with auxiliary data for the upcaller (allow async construction)
+ * - search the process's keyrings
+ * - check the list of keys being created or updated
+ * - call out to userspace for a key if supplementary info was provided
+ */
+struct key *request_key_async_with_auxdata(struct key_type *type,
+					   const char *description,
+					   const char *callout_info,
+					   void *aux)
+{
 	return request_key_and_link(type, description, callout_info, aux,
 				    NULL, KEY_ALLOC_IN_QUOTA);
-
-} /* end request_key_with_auxdata() */
-
-EXPORT_SYMBOL(request_key_with_auxdata);
+}
+EXPORT_SYMBOL(request_key_async_with_auxdata);

security/keys/request_key_auth.c

···
 	}
 
 	key_put(rka->target_key);
+	kfree(rka->callout_info);
 	kfree(rka);
 
 } /* end request_key_auth_destroy() */
···
 	rka = kmalloc(sizeof(*rka), GFP_KERNEL);
 	if (!rka) {
 		kleave(" = -ENOMEM");
+		return ERR_PTR(-ENOMEM);
+	}
+	rka->callout_info = kmalloc(strlen(callout_info) + 1, GFP_KERNEL);
+	if (!rka->callout_info) {
+		kleave(" = -ENOMEM");
+		kfree(rka);
 		return ERR_PTR(-ENOMEM);
 	}
 
···
 	}
 
 	rka->target_key = key_get(target);
-	rka->callout_info = callout_info;
+	strcpy(rka->callout_info, callout_info);
 
 	/* allocate the auth key */
 	sprintf(desc, "%x", target->serial);
···
 
 auth_key_revoked:
 	up_read(&current->request_key_auth->sem);
+	kfree(rka->callout_info);
 	kfree(rka);
 	kleave("= -EKEYREVOKED");
 	return ERR_PTR(-EKEYREVOKED);
···
 	key_put(authkey);
 error_alloc:
 	key_put(rka->target_key);
+	kfree(rka->callout_info);
 	kfree(rka);
 	kleave("= %d", ret);
 	return ERR_PTR(ret);