The ERC20 permit() extension suffers from a significant design oversight. When contracts call permit() they must always take into account it may revert because of a frontrunning attack. More info is available at the Trust Security blog.
Consider using the trustlessPermit() function in this library if the intention is to continue execution when the user allowance is sufficient (As if the permit() executed successfully)
The code in this repo is provided as-is, with no warranty whatsoever. The user takes all responsibility and risks associated with using this library.