Sedum Album has no known hazards and is fine for tortoises as part of a varied diet. Like many succulents it can have a slight laxative effect if eaten in great quantity so it is best not planted within the tortoise enclosure. Often cultivated and grown in the garden but also may be seen growing wild in the countryside.
N.B. Not to be confused with Sedum Acre, which looks very similar but has yellow flowers and should not be fed to tortoises as it contains toxic piperidine alkaloids. If you are not sure that your plant is Sedum Album then it might be wise to refrain from feeding until a positive identification is made.