KEYS: Move the flags representing required permission to linux/key.h

Move the flags representing required permission to linux/key.h as the perm
parameter of security_key_permission() is in terms of them - and not the
permissions mask flags used in key->perm.

Whilst we're at it:

 (1) Rename them to be KEY_NEED_xxx rather than KEY_xxx to avoid collisions
     with symbols in uapi/linux/input.h.

 (2) Don't use key_perm_t for a mask of required permissions, but rather limit
     it to the permissions mask attached to the key and arguments related
     directly to that.

Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Dmitry Kasatkin <d.kasatkin@samsung.com>

include/linux/key.h

@@ -309,6 +309,17 @@ static inline key_serial_t key_serial(const struct key *key)
 
 extern void key_set_timeout(struct key *, unsigned);
 
+/*
+ * The permissions required on a key that we're looking up.
+ */
+#define	KEY_NEED_VIEW	0x01	/* Require permission to view attributes */
+#define	KEY_NEED_READ	0x02	/* Require permission to read content */
+#define	KEY_NEED_WRITE	0x04	/* Require permission to update / modify */
+#define	KEY_NEED_SEARCH	0x08	/* Require permission to search (keyring) or find (key) */
+#define	KEY_NEED_LINK	0x10	/* Require permission to link */
+#define	KEY_NEED_SETATTR 0x20	/* Require permission to change attributes */
+#define	KEY_NEED_ALL	0x3f	/* All the above permissions */
+
 /**
  * key_is_instantiated - Determine if a key has been positively instantiated
  * @key: The key to check.