Merge tag 'keys-request-20190626' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull request_key improvements from David Howells:
 "These are all request_key()-related, including a fix and some improvements:

   - Fix the lack of a Link permission check on a key found by
     request_key(), thereby enabling request_key() to link keys that
     don't grant this permission to the target keyring (which must still
     grant Write permission).

     Note that the key must be in the caller's keyrings already to be
     found.

   - Invalidate used request_key authentication keys rather than
     revoking them, so that they get cleaned up immediately rather than
     hanging around till the expiry time is passed.

   - Move the RCU locks outwards from the keyring search functions so
     that a request_key_rcu() can be provided. This can be called in RCU
     mode, so it can't sleep and can't upcall - but it can be called
     from LOOKUP_RCU pathwalk mode.

   - Cache the latest positive result of request_key*() temporarily in
     task_struct so that filesystems that make a lot of request_key()
     calls during pathwalk can take advantage of it to avoid having to
     redo the searching. This requires CONFIG_KEYS_REQUEST_CACHE=y.

     It is assumed that the key just found is likely to be used multiple
     times in each step in an RCU pathwalk, and is likely to be reused
     for the next step too.

     Note that the cleanup of the cache is done on TIF_NOTIFY_RESUME,
     just before userspace resumes, and on exit"

* tag 'keys-request-20190626' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  keys: Kill off request_key_async{,_with_auxdata}
  keys: Cache result of request_key*() temporarily in task_struct
  keys: Provide request_key_rcu()
  keys: Move the RCU locks outwards from the keyring search functions
  keys: Invalidate used request_key authentication keys
  keys: Fix request_key() lack of Link perm check on found key

4 files changed, 16 insertions, 11 deletions

diff --git a/include/keys/request_key_auth-type.h b/include/keys/request_key_auth-type.h
index 20485ca481f4..36b89a933310 100644
--- a/include/keys/request_key_auth-type.h
+++ b/include/keys/request_key_auth-type.h
@@ -14,6 +14,7 @@
  * Authorisation record for request_key().
  */
 struct request_key_auth {
+	struct rcu_head		rcu;
 	struct key		*target_key;
 	struct key		*dest_keyring;
 	const struct cred	*cred;
diff --git a/include/linux/key.h b/include/linux/key.h
index 8b297b94bfb3..ad17c8f30b4c 100644
--- a/include/linux/key.h
+++ b/include/linux/key.h
@@ -269,23 +269,15 @@ extern struct key *request_key(struct key_type *type,
 			       const char *description,
 			       const char *callout_info);
 
+extern struct key *request_key_rcu(struct key_type *type,
+				   const char *description);
+
 extern struct key *request_key_with_auxdata(struct key_type *type,
 					    const char *description,
 					    const void *callout_info,
 					    size_t callout_len,
 					    void *aux);
 
-extern struct key *request_key_async(struct key_type *type,
-				     const char *description,
-				     const void *callout_info,
-				     size_t callout_len);
-
-extern struct key *request_key_async_with_auxdata(struct key_type *type,
-						  const char *description,
-						  const void *callout_info,
-						  size_t callout_len,
-						  void *aux);
-
 extern int wait_for_key_construction(struct key *key, bool intr);
 
 extern int key_validate(const struct key *key);
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 459d95e4a574..8dc1811487f5 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -892,6 +892,11 @@ struct task_struct {
 	/* Effective (overridable) subjective task credentials (COW): */
 	const struct cred __rcu		*cred;
 
+#ifdef CONFIG_KEYS
+	/* Cached requested key. */
+	struct key			*cached_requested_key;
+#endif
+
 	/*
 	 * executable name, excluding path.
 	 *
diff --git a/include/linux/tracehook.h b/include/linux/tracehook.h
index 09d678433fc0..8446573cc682 100644
--- a/include/linux/tracehook.h
+++ b/include/linux/tracehook.h
@@ -184,6 +184,13 @@ static inline void tracehook_notify_resume(struct pt_regs *regs)
 	if (unlikely(current->task_works))
 		task_work_run();
 
+#ifdef CONFIG_KEYS_REQUEST_CACHE
+	if (unlikely(current->cached_requested_key)) {
+		key_put(current->cached_requested_key);
+		current->cached_requested_key = NULL;
+	}
+#endif
+
 	mem_cgroup_handle_over_high();
 	blkcg_maybe_throttle_current();
 }