My First Haskell word in line finder

I stuck at it, and here is my finished haskell program to find all lines that contain a certain word:

findStrb :: String -> String -> Bool
findStrb key str = if key `isInfixOf` str then True else False


printList :: [String] -> IO ()
printList (x:xs) = do
 putStrLn x
 printList xs


main :: IO ()
main = do
 infile <- readFile "ec2_list"
 printList [x | x <- lines infile, findStrb "kernel" x]