sql: avoid dangling role reference in default privileges

Release note (bug fix): Fixed a bug that could leave behind a dangling
reference to a dropped role if that role had default privileges granted
to itself. The bug was caused by defining privileges such as: `ALTER DEFAULT
PRIVILEGES FOR ROLE self_referencing_role GRANT INSERT ON TABLES TO self_referencing_role`

Author: rafiss

pkg/sql/catalog/catprivilege/default_privilege.go

@@ -118,6 +118,7 @@ func (d *Mutable) GrantDefaultPrivileges(
 			return err
 		}
 	}
+	d.removeRoleIfEmptyPrivileges(role, defaultPrivilegesForRole)
 	return nil
 }
 
@@ -135,14 +136,20 @@ func (d *Mutable) RevokeDefaultPrivileges(
 			return err
 		}
 	}
+	d.removeRoleIfEmptyPrivileges(role, defaultPrivilegesForRole)
+	return nil
+}
 
+// removeRoleIfEmptyPrivilegesc checks if there are any default privileges for
+// the given role remaining on the descriptor. If there are no privileges left
+// remaining and the descriptor is in the default state, the role is removed.
+func (d *Mutable) removeRoleIfEmptyPrivileges(
+	role catpb.DefaultPrivilegesRole, defaultPrivilegesForRole *catpb.DefaultPrivilegesForRole,
+) {
 	defaultPrivilegesPerObject := defaultPrivilegesForRole.DefaultPrivilegesPerObject
-	// Check if there are any default privileges remaining on the descriptor.
-	// If there are no privileges left remaining and the descriptor is in the
-	// default state, we can remove it.
 	for _, defaultPrivs := range defaultPrivilegesPerObject {
 		if len(defaultPrivs.Users) != 0 {
-			return nil
+			return
 		}
 	}
 
@@ -155,12 +162,11 @@ func (d *Mutable) RevokeDefaultPrivileges(
 			!GetRoleHasAllPrivilegesOnTargetObject(defaultPrivilegesForRole, privilege.Schemas) ||
 			!GetPublicHasUsageOnTypes(defaultPrivilegesForRole) ||
 			!GetPublicHasExecuteOnFunctions(defaultPrivilegesForRole)) {
-		return nil
+		return
 	}
 
 	// There no entries remaining, remove the entry for the role.
 	d.defaultPrivilegeDescriptor.RemoveUser(role)
-	return nil
 }
 
 // CreatePrivilegesFromDefaultPrivileges creates privileges for a

pkg/sql/logictest/testdata/logic_test/drop_role_with_default_privileges

@@ -183,3 +183,23 @@ statement ok
 DROP USER IF EXISTS a_user_that_does_not_exist;
 
 subtest end
+
+# Verify that a granting default privileges to the same role the defaults are
+# being defined for has no undesirable side effect.
+subtest default_priv_granted_to_self
+
+statement ok
+CREATE ROLE self_referencing_role
+
+statement ok
+ALTER DEFAULT PRIVILEGES FOR ROLE self_referencing_role GRANT INSERT ON TABLES TO self_referencing_role
+
+statement ok
+DROP ROLE self_referencing_role
+
+query I
+SELECT count(*) FROM crdb_internal.invalid_objects
+----
+0
+
+subtest end