The proper spelling for these words does not contain double consonants.

benefit, benefited, benefiting

cancel, canceled, canceling

travel, traveled, traveling

According to Everything Language and Grammar there is a rule for this:

When a word of more than one syllable ends in a single consonant that is preceded by a single vowel, and the accent is on other than the last syllable of the root word, do NOT double the final consonant before adding the -ed or -ing.