keys: Fix dependency loop between construction record and auth key

In the request_key() upcall mechanism there's a dependency loop by which if
a key type driver overrides the ->request_key hook and the userspace side
manages to lose the authorisation key, the auth key and the internal
construction record (struct key_construction) can keep each other pinned.

Fix this by the following changes:

 (1) Killing off the construction record and using the auth key instead.

 (2) Including the operation name in the auth key payload and making the
     payload available outside of security/keys/.

 (3) The ->request_key hook is given the authkey instead of the cons
     record and operation name.

Changes (2) and (3) allow the auth key to naturally be cleaned up if the
keyring it is in is destroyed or cleared or the auth key is unlinked.

Fixes: 7ee02a316600 ("keys: Fix dependency loop between construction record and auth key")
Signed-off-by: David Howells <dhowells@redhat.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

1 files changed, 1 insertions, 12 deletions

diff --git a/security/keys/internal.h b/security/keys/internal.h
index 479909b858c7..8f533c81aa8d 100644
--- a/security/keys/internal.h
+++ b/security/keys/internal.h
@@ -186,20 +186,9 @@ static inline int key_permission(const key_ref_t key_ref, unsigned perm)
 	return key_task_permission(key_ref, current_cred(), perm);
 }
 
-/*
- * Authorisation record for request_key().
- */
-struct request_key_auth {
-	struct key		*target_key;
-	struct key		*dest_keyring;
-	const struct cred	*cred;
-	void			*callout_info;
-	size_t			callout_len;
-	pid_t			pid;
-} __randomize_layout;
-
 extern struct key_type key_type_request_key_auth;
 extern struct key *request_key_auth_new(struct key *target,
+					const char *op,
 					const void *callout_info,
 					size_t callout_len,
 					struct key *dest_keyring);