Yes, its safety used as a food additive has been approved by the U.S. Food and Drug Administration (FDA), European Food Safety Authority (EFSA),  Joint FAO/WHO Expert Committee on Food Additives (JECFA), as well as other authorities.

FDA
FDA has approved the application of L and DL malic acid in food, except the baby food, at levels not to exceed good manufacturing practice.

It is generally considered safe (GRAS) and can be used in food as a flavor enhancer, flavoring agent and adjuvant, and pH control agent.

The following are the uses and the maximum level approved by FDA (12):

Food Application
Maximum uses Level
Nonalcoholic beverages    3.4%
Chewing gum    3.0%
Gelatins, puddings, and fillings    0.8%
Hard candy    6.9%
Soft candy    3.0%
Jams and jellies    2.6%
Processed fruits and fruit juices    3.5%
All other food categories    0.7%

http://www.chinafooding.com/L-Malic_Acid