Merge tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs

Pull keyring ACL support from David Howells:
 "This changes the permissions model used by keys and keyrings to be
  based on an internal ACL by the following means:

   - Replace the permissions mask internally with an ACL that contains a
     list of ACEs, each with a specific subject with a permissions mask.
     Potted default ACLs are available for new keys and keyrings.

     ACE subjects can be macroised to indicate the UID and GID specified
     on the key (which remain). Future commits will be able to add
     additional subject types, such as specific UIDs or domain
     tags/namespaces.

     Also split a number of permissions to give finer control. Examples
     include splitting the revocation permit from the change-attributes
     permit, thereby allowing someone to be granted permission to revoke
     a key without allowing them to change the owner; also the ability
     to join a keyring is split from the ability to link to it, thereby
     stopping a process accessing a keyring by joining it and thus
     acquiring use of possessor permits.

   - Provide a keyctl to allow the granting or denial of one or more
     permits to a specific subject. Direct access to the ACL is not
     granted, and the ACL cannot be viewed"

* tag 'keys-acl-20190703' of git://git.kernel.org/pub/scm/linux/kernel/git/dhowells/linux-fs:
  keys: Provide KEYCTL_GRANT_PERMISSION
  keys: Replace uid/gid/perm permissions checking with an ACL

1 files changed, 24 insertions, 6 deletions

diff --git a/fs/nfs/nfs4idmap.c b/fs/nfs/nfs4idmap.c
index 1e7296395d71..69679f4f2e6c 100644
--- a/fs/nfs/nfs4idmap.c
+++ b/fs/nfs/nfs4idmap.c
@@ -72,6 +72,25 @@ struct idmap {
 	const struct cred	*cred;
 };
 
+static struct key_acl nfs_idmap_key_acl = {
+	.usage	= REFCOUNT_INIT(1),
+	.nr_ace	= 2,
+	.possessor_viewable = true,
+	.aces = {
+		KEY_POSSESSOR_ACE(KEY_ACE_VIEW | KEY_ACE_SEARCH | KEY_ACE_READ),
+		KEY_OWNER_ACE(KEY_ACE_VIEW),
+	}
+};
+
+static struct key_acl nfs_idmap_keyring_acl = {
+	.usage	= REFCOUNT_INIT(1),
+	.nr_ace	= 2,
+	.aces = {
+		KEY_POSSESSOR_ACE(KEY_ACE_SEARCH | KEY_ACE_WRITE),
+		KEY_OWNER_ACE(KEY_ACE_VIEW | KEY_ACE_READ),
+	}
+};
+
 static struct user_namespace *idmap_userns(const struct idmap *idmap)
 {
 	if (idmap && idmap->cred)
@@ -208,8 +227,7 @@ int nfs_idmap_init(void)
 
 	keyring = keyring_alloc(".id_resolver",
 				GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred,
-				(KEY_POS_ALL & ~KEY_POS_SETATTR) |
-				KEY_USR_VIEW | KEY_USR_READ,
+				&nfs_idmap_keyring_acl,
 				KEY_ALLOC_NOT_IN_QUOTA, NULL, NULL);
 	if (IS_ERR(keyring)) {
 		ret = PTR_ERR(keyring);
@@ -287,11 +305,13 @@ static struct key *nfs_idmap_request_key(const char *name, size_t namelen,
 		return ERR_PTR(ret);
 
 	if (!idmap->cred || idmap->cred->user_ns == &init_user_ns)
-		rkey = request_key(&key_type_id_resolver, desc, "");
+		rkey = request_key(&key_type_id_resolver, desc, "",
+				   &nfs_idmap_key_acl);
 	if (IS_ERR(rkey)) {
 		mutex_lock(&idmap->idmap_mutex);
 		rkey = request_key_with_auxdata(&key_type_id_resolver_legacy,
-						desc, NULL, "", 0, idmap);
+						desc, NULL, "", 0, idmap,
+						&nfs_idmap_key_acl);
 		mutex_unlock(&idmap->idmap_mutex);
 	}
 	if (!IS_ERR(rkey))
@@ -320,8 +340,6 @@ static ssize_t nfs_idmap_get_key(const char *name, size_t namelen,
 	}
 
 	rcu_read_lock();
-	rkey->perm |= KEY_USR_VIEW;
-
 	ret = key_validate(rkey);
 	if (ret < 0)
 		goto out_up;