Q: My visa expired, but my I-94 is still valid. Am I out of status?
A: No, not because the visa expired. Your visa is what you use to ask for entry into the United States. Once you are here, your I-94 controls how long you were admitted for, unless your record shows D/S. You still have to follow the rules of your status. You can check your latest I-94 at https://i94.cbp.dhs.gov/search/recent-search. If you leave the United States, you will usually need a valid visa to come back unless an exception applies.
Source: U.S. Department of State. What the Visa Expiration Date Means: https://travel.state.gov/content/travel/en/us-visas/visa-information-resources/visa-expiration-date.html