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>
diff --git a/security/keys/permission.c b/security/keys/permission.c
index efcc0c8..732cc0b 100644
--- a/security/keys/permission.c
+++ b/security/keys/permission.c
@@ -28,7 +28,7 @@
  * permissions bits or the LSM check.
  */
 int key_task_permission(const key_ref_t key_ref, const struct cred *cred,
-			key_perm_t perm)
+			unsigned perm)
 {
 	struct key *key;
 	key_perm_t kperm;
@@ -68,7 +68,7 @@
 	if (is_key_possessed(key_ref))
 		kperm |= key->perm >> 24;
 
-	kperm = kperm & perm & KEY_ALL;
+	kperm = kperm & perm & KEY_NEED_ALL;
 
 	if (kperm != perm)
 		return -EACCES;